MSK MR example






-Acromion: Type I flat, II curved, III hooked (spur), IV convex (@sagittal); Lateral downsloping or low lying acromion w/ respect to clavicle (@coronal)

-AC (degen arthrosis, capsular hypertrophy, inf spurring, mass effect on musculotend jct, geyser synovial cyst)

-CAL=Coracoacromial ligament hypertrophy (@sagittal)—mimics inferior acromial spur

-CCL=Coracoclavicular lig (trapezoid lig—ant & lat to conoid lig which is more imp) along coracoclavicular interval: best seen on cor and sag

-Os Acromiale @axial (fused by age25)                    

-Muscle overdevelopment (hypertrophy)


ROTATOR CUFF (sag and cor T2 FS not PD FS)—look for intact fat plane btwn acromion and rotator cuff on cor T1


-don’t have synovial sheath; Magic angle 1cm prox to insert supraspin (short TE T1/PD/GRE, except T2)

-Tendinopathy/Tendinosis (SIT inserts on Greater Tub and Subscapsularis inserts Lesser Tub)

-Supraspinatus (ant-sup) and deltoid abduct; infraspinatus (post-sup) and teres minor (post-inf) ext rot; subscapularis (ant) int rot

-Foot plate and adjacent bare area (medial) on greater tuberosity             

-conjoined tendons of supra and infraspinatus

-Tendinopathy vs Partial tear (undersurface or articular surface>bursal surface; rim-rent=distally at bony attachment site)

-Full thickness tear (focal perforation)           

-Interstitial /longitudinal tear or delamination (intramuscular cyst)

-Complete tear (partially displacement or retraction of musculotendinous jct which should be just lat to AC jt)       

-Massive cuff tear

-SUBSCAPULARIS: 4tendons (superior tendinous slip aka biceps stabilizer; upper intramuscular tendon; remaining intramuscular tendon; muscular insertion)

-HADD (near supraspin; darker than tendon; blooms on GRE)      

-Degen cystic changes at greater tuberosity       

-Bursa Subacromial/Subdeltoid vs Subcoracoid (not comm w/ jt but comm w/ subacr/subdelt bursa 20%; inf to coracoid; ant to subscap tendon)ßnot same as subscapularis recess 

-Rotator interval (@sagittal btwn supraspin&subscap) contains biceps; CHL+SGHL forms biceps pulley; patulous/torn if athroscopy/disloc

-Muscular atrophy (@T1 fatty infiltration “marbled”): disuse vs denervation (acute>2wks to1year=edema; chronic>1year=fatty atrophy)


LABRUM/CAPSULE (@PD FS cor and axial)—triangular>rounded; myxoid degen with aging


-Anterior labrum (describe signal abnl, location, extent, assoc biceps anchor abnl, assoc cartilaginouss abnl) 

-Biceps labral sulcus or art cartilage undercutting = seen on coronal;  sublabral recess or sublabral foramen = seen on axial

-SLAP (extend post beyond biceps insertion on sup labrum;look for detached labrum;torn biceps-labral anchor;partial/full thick tear)

-Bankart (complete detached anterior-inferior labrolig complex w/ torn periosteum; loss of triangular shape and incr signal)

-Perthes (nondisplaced tear of the anteroinferior labrum; similar to ALPSA but labrum is scarred down to its original site)

-ALPSA (periosteal sleeve avulsion + labrolig complex displaced medially; periosteum stripped but not torn off; lot of scar if chronic)

-GLAD (non-displaced anteroinferior labral tear w/ chondral defect from impaction-type injury)

-Posterior labrum (6-11o’clock)= Reverse bankart and Bennett (calc of posterior joint capsule or IGHL)ßpost labrum may be nl blunted

-Paralabral cyst (more common with posterior labral tear)

-Glenohum lig @axial and sagittal (labrolig complex; SGHL curvilinear along coracoid ant to biceps, MGHL post to subscap tendon and absent in 30% w/o BUFORD, IGHL most imp with ant/post band ax pouch/recess)

-Adhesive capsulitis <7cc (small capsular recess, decr jt capacity, thickened serrated capsule>4mm, thick IGHL at ax pouch or CHL in rot int)

-ABER view good for inferior labrum (ant is on opposite side as coracoid)—posterosuperior (relaxed) and anteroinferior (under tension) labrum; may diagnose Perthes; also eval undersurface of suprapsinatus and infraspinatus; can look for posterior subluxation b/c under tension; can diagnose “posterior-superior internal impingement” (which includes post labral tear, greater tub cystic changes, undersurface tear of IS)


BONE/CARTILAGE (cartilage best on PD FS)


-Marrow signal                

-Cartilage (hyaline): thinning, fraying or superficial fibrillation, partial thickness defect, full-thickness defect

-Bankart (ant-inf) / Hillsach’s (on top 3 axial views posterolaterally at or above coracoid) vs Reverse Bankart (post) / Trough (anteromed)

-Humeral head subluxation (acromiohumeral interval)     

-Capsular laxity (Type III medial capsular insertion >1cm medial to labrum @axial)

-Subcoracoid impingement (if distance btwn coracoid and humeral head is <1cm on axial with edema or cystic changes of lesser tuberosity)

-Greater tuberosity: horizontal facet (sup-ant)=supraspinatus; oblique facet (middle)=supra/infraspinatus; posterior/vertical facet (inf)=teres minor

-Glenoid bare spot (kids10-20yo only): range in size from 2.5-9mm; usually center of glenoid

-Little league shoulder (proximal lateral humeral physis BM edema; widening of physis; +/- metaphyseal fragmentation)


LH Biceps tendon (axial and cor)


-Long head in bicipital grooveà rotator intervalàunder supraspinatusàsup labrum “biceps-labral complex/anchor” @supraglenoid tubercle —seen on anterior slices on coronal; short head of bicepsàcoracoid

-Tendinopathy vs tenosynovitis (remember comm. w/ joint) vs tear (assoc w/ supraspinatus tears); focal stenosing tensynovitis (loc fluid+septa)

-Located within Rotator interval (medial and lateral aspects of coracohumeral lig  and the SGHL keep it in place) 

-Sublux vs disloc (perched vs anteromed vs medial; biceps located deep vs sup to subscap), empty bicipital groove (BICEPS PULLEY medially=subscap+ SGHL/medial CHL and laterally=lateral CHL)

-Postop: tenotomy (cut) vs tenodesis (re-attach)





-Loose body (subscap recess)  

-Avulsion of IGHL=HAGL/BAGHL (bony avulsion)    

-Suprascapular notch (SS,IS) vs Spinoglenoid notch (IS) nerve entrapment

-Parsonage turner (acute viral brachial neuritis with multiple muscle edema SS, IS, deltoid)

-Quadrilateral space syn (located post axilla; btwn teres major/minor and long head triceps; axillary nerve; fatty atrophy deltoid, teres minor)

-Adenopathy or Chest wall / Pulmonary lesion      

-Deltoid muscle/tendon slip (inserts on acromion)

-Post-op shoulder (anchors, metal shaving, scar, granulation tissue=lowT1/hiT2 during 1st year)

-PECTORALIS MAJOR: clavicular head (sup; arises from medial 1/3 to 2/3 of clavicle) and sternal head (inf and deep; arises from manubrium/sternum/ribs) of pec major unite to form bilaminar tendon; tendon is curvilinear low-signal band inserting onto the lateral ridge of the bicipital groove of proximal humerus; injury may only involve clavicular or sternal head or both; low or high-grade partial tear vs complete tear; location=at myotendinous jct vs partial/complete periosteal stripping/avulsion at humeral insertional site w/ or w/o retraction

-PECTORALIS MINOR: origin 3/4/5th anterior ribs and insertion is coracoid process of scapula


Glenohumeral instability (prefer MR arthrogram)

-Glenoid: labral abnl (bankart, perthes, or ALPSA), shallow/dysplastic glenoid

-Capsular: thickened; laxity/tear (type III ant capsule inserts >1cm med to labrum capsular @axial)

-Humeral: HAGL or BHAGL         

-Rotator interval abnormality           

-Prior dislocation; deficient or torn GHL

TUBS=traumatic unidirectional bankart surgery; AMBRI=atraumatic multidir bilat rehab inf capsular shift







MENISCI (PD w/ FATSAT): 2 bowtie for body of meniscus on sag view (4-5mm slices)


-MEDIAL MENISCUS (post horn > ant horn)

-LATERAL MENISCUS (discoid ≥3 bowties on sag and extends into IC notch on coronal)—ant horn merge with ACL and may be striated in this region; posterior horn medially may have magic-angle artifact


-Tear types (on at least 2 images and 2 planes):

     -INTRASUBS DEGENERATION (ddx: radial, CPPD, magic angle, meniscal cyst): grade I=globular signal, grade II=linear 

      signal (does not extend to any surface), grade III=tear extends to surface

     -HORIZONTAL (extend to sup/inf art surface, apex, or periphery)

     -note: peripheral tears may be assoc w/ menisco-capsular separation—don’t confuse with interstitial bursa btwn post horn 

      of medial meniscus and capsule OR gap btwn post horn of lateral meniscus and popliteus tendon; more common w/ ACL 


     -VERTICAL tears (occur at periphery; may be oriented obliquely)

longitudinal (no displaced fragment; equidistant from periphery on all sag images; may extend to articular surface)

bucket handle (attached on both ends but displaced; only one bowtie on sag; double PCL or ant flipped meniscus)

flap (displaced flap attached only on one end; undersurface tear may displace into medial gutter; seen on coronal)

     -RADIAL/FREE EDGE (only one bowtie on sag)=partial/complete

radial (blunted free edge; perpendicular to edge of meniscus; seen in post horn/body)

parrot beak (like radial tear, oriented obliquely “comma”)

root tear (near IC notch)

     -COMPLEX tear (branching); MASCERATED

     -Peripheral extrusion (aka subluxation)—extending into superior/inferior gutter


-Paramensical cyst (may result in surface bone erosion)   

-Transverse lig 40% (seen ant, from AHMM to AHLM, surrounded by fat)

-Meniscofemoral lig—oblique from PHLM to med fem condyle; ant (more-common “Humphry”) or post (“Wrisberg”) to PCL

-Meniscal ossicle (usually PHMM)

-Meniscal flounce (normal variant undulation/wavy periphery of meniscus)

-Meniscal cyst

-Partial meniscectomy (truncated) if prior repair




-ACL (parallel to or steeper than roof of IC notch on sag; interspersed hi signal fat near tibial attach; peripheral PHLM tears common)        

     -Anteromedial and posterolateral bands; tibial attachment is stronger than femoral attachment

     -ACL sprain or partial tear—increased signal+laxity (correlate for ACL insuff); Tears mid>prox>distal; Mucoid degen 


     -O’donahue triad (ACL tear, MCL injury, medial meniscus) + patellar dislocation (medial retinaculum)   

     -Assoc w/ posterolat tibia & anterlat femoral condyle kissing contusion, OC fx OR tibial eminence avulsion fx (r/o 

     transverse lig not displaced underneath the avulsion fx) OR segond fx (posterolat capsular avulsion fx)—assoc with 

     posterolateral corner injury


ACL graft

-some signal (less than fluid) 1st 2yrs

-tibial tunnel parallel to roof of IC notch “straight and back”

-tibial tunnel oriented parallel to BS line and intraart opening post to where BS line meets tibia on sag

-if tibial tunnel too antà roof impingement on IC notch; if too postàgraft instability

-femoral tunnel where posterior cortex meets physeal scar (11 or 11’oclock position on coronal view of right or left knee)

-inf femoral tunnel located at intersection of line along post fem cortex and line along interchondylar notch (blumensaat line) on sag

-Arthrofibrosis=focal (Cyclops) vs diffuse

-cystic degen (ganglion along tunnel)—as long as graft intact, this is not a big issue

-loose bodies


-PCL (thickening+intermed signal is abnl; usually tears off tibial attachment); not question mark (PCL buckling sec to ACL injury)

-MCL (superficial band + fat/bursa + deep band firmly attached to meniscus; also POL=post oblique lig; look for meniscocapsular separation; sprain=signal superficial to MCL, partial tear=thickening or signal within MCL but overall intact; complete disruption)

-LCL (IT band anteriorly onto tibial Gerdy’s tubercle; FCL+Biceps femoris form “conjoined tendon” and inserts on fibular head)

-MED/LAT RETINACULUM (axial; med ret injury w/ patellar disloc/reloc injury)






     -PATELLAR TENDON (on sag; pre-patellar/deep infra-patellar bursitis; Jumper’s)

     -IT BAND (axial and coronal—fluid on both sides at level of fem condyle)

     -POPITEAL TENDON (sag; from lat fem condyle inferiorly to btwn PHLM and jt capsule; bursitis vs tear)

     -PES ANSERINE (sartorious, gracilus, semitendinosis; bursa btwn MCL and pes anserine below joint line)ßcoronal       

     (inserts quite anteriorly below joint line upon medial tibial metaphysis)

    -Posterolateral corner syndromeàsuspect if tear of two or more (FCL/biceps femoris conjoined tendon “V”+ arcuate lig + 

     pop tendon=arcuate complex; and popliteofibular lig) plus PCL>ACL tear; may or may not have edema in fibular head;     

     emergency call ortho!! Need to operate <1wk

-MUSCLE (plantaris tendon tear aka “tennis leg”)


BONE/CARTILAGE: (cartilage on PD both with fatsat)



-anatomy: intercondylar notch/fossa; intercondylar tibial eminence (media/lateral tibial spines); trochlear groove of femur and patellar apex; anterior tibial tuberosity

-bone bruise vs osteochondral fx     

-femoral trochlear dysplasia (shallow<3mm)   

-SONK (insuff fx medial fem condyle)

-avulsion fx may not be assoc with sig marrow edema unlike contusion or impacted fx

-patellar dislocation/relocation injury (look for chondral defect, loose bodies, shallow trochlear groove, medial retinaculum and medial patellofemoral lig tear; risk of patellofemoral instability=femoral trochlear hypoplasia, increased trochlear tubercle distance, lateral patellar shift)

-OCD: stable vs unstable (fluid signal undercutting lesion and/or multiple T2 cyst surrounding lesion; BM edema not 


-Anatomic axis: Normal tibiofemoral angle 0-10deg; varus <0deg; valgus >10deg


-Patellar tendon lateral femoral condyle friction syndrome (patellar tracking abnormality): superolateral Hoffa fat pad impingement btwn inf patella and lat femoral condyle;

DYNAMIC CT=image knee in full extension (0deg) and varying deg of flexion (15/30/60/90deg); lateral patellar tilt=negative “lateral patellar angle” with early flexion <30deg (normal is positive angle)àwith further flexion subluxation may improve or worsen; lateral patellar subluxation/shift (AC/AB) reported in percentage; basically significant tilt or subluxation by 20deg of flexion is mal-alignment; patella normally may sit lateral to trochlea at full extension but with flexion it engages the trochlea and should be centered without tilt; 



-if >1.5cmàgrade; chondral degeneration vs defect; post-op: chondral thinning w/ subchondral microfx

-PF JOINT (patellar eminence or median ridge, and trochlear groove)     

-FT JOINT (ant/post WB surface; interchondylar notch of femur; medial/lateral tibial eminence or spine)

               -I=normal (softening), II=fraying/abnl signal, III=fissure/ulceration/fragmentation, IV=full thick defect

               -3D SPGR w/ fatsat (TR60, TE5, flip angle 40) 6min 

-Microfractures (lenticular defects)—prior cartilage repair





-LOOSE BODIES            


               -SYNOVIAL PLICAE (thickened medial vs supra/infrapatellar vs lateral plica; look for any synovitis, PF chondral     

  defect, or hoffitis)

               -BAKER’S CYST (“M&M” medial head gastroc and semimembranous tendon; can be septated or complicated or 

               partially ruptured or leaking)

-BURSITIS (post horseshoe “semimembranous-TCL” located medial knee; Pes anserine bursa located more distally anteriorly and superficially to SMTCL bursa; popliteal bursa; prepatellar vs superficial/deep infrapatellar bursa; FCL-bicep femoris bursa located laterally)

-HOFFA FAT (hoffitis)

-HOFFA FAT MASS ( lipoma, hemangioma, synovial chondromatosis, focal villonodular synovitis, ganglion cyst, osteochondroma, chondrosarcoma)                                          




-popliteal aneurysm

-venous thrombosis (loss of pulsation artifact)

-Cystic adventitial disease (T2 bright cystic changes of popliteal artery wall with stenosis)






TENDONS: (dark on all sequences except distal PTT and Achilles)



-Tibialis anterior (medial and largest; abnormal in “grumpy old men” with DM or Gout; may appear mass-like), Extensor hallucis longus, Extensor digitorum longus


-MEDIAL FLEXOR (PASS THRU TARSAL TUNNEL; some fluid in synovial sheath is normal if not circumferential)

-tom=PTT (most anterior; twice the size of other two, tendon sheath ends 1-2cm prior to NAVICULAR INSERTION--fluid here is not uncommon “peritendonitis”, elsewhere called “tenosynovitis”; severe tendinosis vs partial tear if 5x thickened with internal high T2 foci; type II tears if tendon smaller or same size as  FDL; PTT dysfunction in middle-aged women leads to flat-foot and assoc medial malleolar edema; passes beneath medial mall as a pulley; may dislocate anteromedial to medial mall with tear of flexor retinaculum; higher incidence of tear with acc navicular ossicle)

-dick=FLEX DIGIT LONGUS (rarely injured; under foot like fan; cris-crosses with FHL under foot at knot of Henry; INSERTS DISTAL PHALANX 2-5th TOES)

               -posterior tibial A/N/V

-harry=FHL (COMM W/ JT; passes thru fibrosseous tunnel btwn lat and medial talar tubercles; under ses tali of calcaneus; injury seen in athletes with extreme plantar-flexion; injury accentuated by os trigonum “stenosing tenosynovitis” loculated fluid with septa; tenosynovitis if fluid> ankle eff; magic angle vs tenosynovitis as it goes btwn sesamoids along great toe; INSERTS 1st DISTAL PHALANX)


-LATERAL PERONEUS (behind and underneath fibula as pulley; PB ant and PL post to peroneal tubercle of calcaneus)

-PB ANTERIOR AND MEDIAL TO PL; share common tendon sheath to level of tibial tip; may dislocate laterally from behind fibula with detachment of superior retinaculum; look for shallow retromalleolar groove of fibula; magic angle under fibula

-PB (FLAT or cresenteric with posterior concavity; ATTACHES TO 5th MT BASE; injured more commonly than PL; may have longitudinal tear “boomerang” or C-shaped appearance with medial/lateral limbs and PL in center--symptomatic in young adults or asymp in elderly; “PB split” longitudinal tear vs bifurcated brevis vs accessory peroneus quartus muscle)

-PL (distal tear at level of cuboid tunnel; may be located post to or anterior to peroneal tubercle of lat calcaneus; INSERTS ONTO PLANTAR ASPECT OF 1st MT BASE OR PLANTAR ASPECT OF MED CUNIEFORM)

               -Peroneal quartus (accessory muscle)



-ACHILLES (no tendon sheath; “smiling” concave or flat anteriorly below soleus insertion; parallel and uniform thickness ~7mm AP on sagittal; rupture ~2-6cm proximal to calcaneal insertion; retrocalcaneus bursa may have small amount of fluid <6mm; kager’s fat inflam/edema)

-TEAR=interstitial vs partial vs complete

-TENDINITIS= paratendonitis à peritendonitis tear (early tendonitis may be seen as edema post to tendon along paratenon—analagous to synovitis “paratenonitis”; later peritendinous edema “peritendonitis”)

-TENDINOSIS=fusiform thickened tendon with or w/o internal signal

-haglunds=post-sup calcaneus prom (pump’s bump) +insertional Achilles tear/tendinosis +retrocalcaneal +retroachilles bursitis

-round/ovoid internal high T2 signal may represent interstitial tear or mucoid degen; striated/stippled Xanthoma in familial hypercholestoremia; enlarged/heterogenous/wavy=partial tear;

-PLANTARIS (90%, skinny tendon medial and anterior to Achilles, may insert on Achilles or post calcaneus)

-ACC SOLEUS MUSCLE (btwn Achilles and FHL tendon)





-LATERAL (BEST ON AXIAL except calcaneofibular):  

     -HIGH ANKLE LIG (TIB/FIB + inteross memb = syndesmosis)

     -ant and post TALOFIB(ATAF#1=anterolat gutter, post#3=concave mall fossa)

               -acute ATAF tear=edema/torn; chronic ATAF tear=thickened

     -CALCANEOFIB (#2; difficult to see; use both cor and axial; deep to peroneal tendons)


-MEDIAL (superficial and deep DELTOID lig) deep deltoid lig=striated on coronal

    -TIBIONAV—not well seen, TIBIOCALC (ses tali), TIBIOTALAR (striated)

    -SPRING (btwn s.tali and navicular)—important for support

    -located deep to flexor tendons; loss of normal striation of deltoid lig may mean chronic contusion/tear




-TALAR DOME OCD (lesion size; surrounding BM edema &  cyst; cortical-cartilag component; fluid-undercutting ”unstable frag”; articular surface incongruity or depression; loose body)

-SUBTALAR JT (3facets on talus and calc but only 2 subtalar jt; ant and middle facet make up ant subtalar jt=talocalcaneonavicular jt ; post facet make up post subtalar jt)

-TARSAL COALITION (CN>TC>TN; TC occurs btwn s.tali and middle facet of subtalar jt; osseous/fibrous/cartilagenous or combo)

-OS TRIGONUM SYNDROME (FHL; post ankle impingement) or POST ANKLE IMPINGEMENT (edema within posterior lateral talar tubercle or os trigonum; may involve FHL)

-Neuropathic joint: hypointense BM on T1 and T2 (chronic); 4D’s (density, destruction, dislocation/disorganized, debris/loose bodies)

-OM: ST ulcer/cellulitis/abscess w/ early periostitisàlater cortical bone disruption or osteolysis w/ 30-50% bone loss=specific; periostitis or BM edema alone may be reactive “osteitis”; MOST SPECIFIC=loss of dark cortex with abnl cortical signal; Gad not necessary but useful to identify ST abscess or dead bone=sequestrum; +CRP in 98% but WBC not reliable; culture often –ve; usually hematogenous spread in kids (starts in subphyseal metaphysis and spread to subperiosteum or intra-articular but in neonates can spread to epiphysis across physis); brodie’s abscess=subphyseal lytic lesion in metaphysis with draining sinus; chronic OM can have draining sinus in adults

-AVN or Osteonecrosis: serpentine double line sign on T2 (dark sclerotic zone with parallel bright zone of granulation) or diffuse low signal on T1/T2 (Navicular=Kohler kids, Mueller-Weiss in adults; Frieberg’s; Lat aspect of navicular secondary to stress fx; lateral sesamoid)

-TIBIAL STRESS REACTION OR SHIN SPLINTS: Medial Tibial Stress Syndrome (MTSS) gradeI=periosteal edema, gradeII=also endosteal/BM edema on T2, gradeIII=also abnl BM signal on T1, gradeIV=fx line visible

-TIBIAL STRESS INJURY OR FRACTURE: endosteal and periosteal edema; on axial imaging may see linear dark fracture cleft bordered by callus; also see adjacent deep subcut edema; gradeI=periosteal edema (shin splint), gradeII=plus BM edema on T2 (early stress injury), gradeIII=BM edema also on T1, gradeIV=visible cortical fx line—dark on all seq (stress fx)

-Longitudinal stress fx= rare

-Non-specific BM edema: may be stress reaction/response vs contusion (bone bruise)


TARSAL TUNNEL (medial under ses tali; flexor retinaculum)

SINUS TARSI (cone-shaped wide lateral; interosseous lig med and cervical lig lat; fat; don’t make this dx in setting of acute trauma) ANTEROLAT GUTTER (synovitis/fibrosis deep to ant tibiofib lig+ATAF)








-PLANTAR FASCITIS (>4mm; fascial/perifascial edema, calcaneal tuberosity edema)  

-PLANTAR FASCIAL TEAR (focal partial vs complete; components=Medial component, Lateral component, Central component, Digital bands)

-PLANTAR FIBROMATOSIS (enhancing low T1/T2) 

-Morton’s neuroma (give Gad; teardrop or dumbbell shaped; low to int T2; best seen on coronal T1; inferior along 3rd web space or btwn 3rd/4th interMT space and less commonly along 2nd web space; plantar digital nerve perineural fibrosis) w/ or w/o intermetatarsal bursitis (high T2; vertical inbtwn MT)ßddx=plantar plate injury

-Enthesitis (enhancement surrounding distal tendons and at insertion site; seen with seronegative spondylo-arthropathies)

-Medial plantar nerve entrapment (aka jogger’s foot; usual site of compression is at knot of Henry where FDL and FHL criss-cross) 








supine vs prone (superman) imaging

Coronal for collateral lig and bones

Sagittal for biceps/triceps tendons and cartilage

Axial for muscles and nerves

FABS (flexed elbow, abducted shoulder, and supinated forearm) axial/sag PD for biceps

Arthrogram (do for OCD, loose bodies, undersurface tears of radial/ulnar collateral lig)




-Capitellar pseudodefect (posterior non-articular capitellum has abrupt notch-like slope on coronal image)

-Bare area “trochlear cortical notch or groove” (devoid of cartilage) and “transverse trochlear ridge” of olecranon seen on sagittal

-Radiocapitellar joint

-Ulnohumeral joint (ulnar coronoidàtrochlea; olecranon process)

-Prox RUJ (radial head rotates w/in sigmoid notch of ulna for pronation/supination)


·        Panner’s (5-12yo; fragmented/mottled capitellar epiphysis w/ patchy low signal T1 w/ abnl contours & no loose body; resolve upon F/U w/ no residual deformity)

·        OCL (12-16yo; anterior convex aspect of capitellum in dominant hand of thrower due to chronic microtraumaà assess for stability of fragment, loose body, and overlying hyaline cartilage integrity; F/U shows residual deformity)—unstable if surrounding T2 signal/cyst deep to fragment/T2 edema in fragment (do arthrogram)

-MIMIC=pseudodefect posterior non-articular capitellum has abrupt notch-like slope on coronal image (but no edema)

·        Epicondylitis (adults; medial>lateral; implies partial tear/tendinopathy); Apophysitis (kids; widening of physis on plain film c/w SH-I fx; “Little league” elbow)

·        Stress fx (middle third of olecranon)

·        Posterior dislocation (assoc w/ tear of radial collateral lig and common extensor tendon)


LIGAMENTS (coronal)


-Radial (lateral) collateral ligaments (“tennis elbow”; generally not torn unless posterior dislocation vs after radial head resection vs after common extensor tendon or tennis elbow release) RESIST VARUS STRESS

·        RCL (radial collateral lig; coronal; triangular; arises from anterior aspect of epicondyle and inserts onto annular lig &  fascia of supinator muscle; may be hard to distinguish from overlying common extensor tendon unless joint effusion or arthrogram)

·        LUCL (lateral ulnar collateral lig; coronal; most important posterolateral stabilizer; located posterior and superficial; oriented obliquely; inserts onto crista supinatoris of ulna; absent in 10%; tear leads to posterolateral rotatory insufficiencyàtransient rotatory sublux ulnohumeral jt and secondary sublux/disloc of radiohumeral jt)

·        Annular ligament (axial; arises and inserts on sigmoid notch of ulna; primary stabilizer of prox RUJ)

·        Evaluate integrity of common extensor tendon (superficial to radial collateral lig)

·        Lateral synovial fringe (radiocapitellar meniscus; seen on coronal)

·        Tennis elbow (radial collateral lig injury + common extensor tendon injury esp partial avulsion of extensor carpi radialis brevis + lat epicondylitis)—MIMIC=radial nerve entrapment


-Ulnar (medial) collateral ligaments—more commonly injured (even though lateral epicondylitis more common) RESIST VALGUS STRESS

·        Anterior bundle UCL (thicker and most imp; coronal; prox flared and distal tapered; from epicondyle to sublime tubercle of coronoid process which can avulse off; should be taut; normal to have sl signal w/in prox flared portion; midsubstance tear> distal>proximal; chronic degen or remodelling if thickened +/- dystrophic calc; partial-thickness deep undersurface tears very difficult w/o gadàsubtle fluid beneath distal extent of bundle separating lig from bone “T-sign” on coronal c/w partial tear or stripping)—tears treated surgically only in elite athletes aka Tommy John’s surgery (docking technique w/ autograft)

·        Other 2 bundles not well seen (together form floor of cubital tunnel)

        -Posterior bundle (fan-shaped; from epicondyle to olecranon; best seen when elbow flexed at 90deg)

                           -Transverse bundle (least imp; horizontal from olecranon to coranoid; join inf aspects of anterior and posterior bundles)

·        Evaluate integrity of common flexor tendon

·        Golfer’s elbow (ulnar collateral lig injury + common flexor tendon injury + medial epicondylitis; “Little league elbow”=avulsion of medial epicondylar apophysis) 

Valgus instability (etiologies include: medial epicoylopathy; ulnar neuropathy; posteromedial olecranon impingement +/- loose bodies; radiocapitellar overload w/ OCD) 


MUSCLES (axial and sagittal)


Medial epicondylitis=Golfers and Lateral epicondylitis=Tennis elbow: partial tear of common flexor/extensor tendons and tendinosis (possible avulsion).

In children, medial apophysitis (Little league elbow): edema within medial epicondylar apophysis +/- widened physis (aka SH I fracture).

·        Anterior compartment

-Biceps brachii tendon (short head inserts distally on radial tuberosity with larger footprint while long head inserts slightly proximally with smaller footprint; no synovial lining; bicipital aponeurosis aka lacertus fibrosus keeps it in place at antecubital fossa; distal tendon covered by extrasynovial partenon; radiobicipital bursa underneath it at radial tuberosity normally not visualized; partial tear less common than complete tear; injury occurs with abrupt overloading of muscle at midlfexion; complete tear at radial tuberosityàlook for “popeye” prox retraction and integrity of aponeurosis; may not retract unless aponeurosis is torn)—mimickers of biceps tear include biceps tendonitis vs radiobicipital bursitis (usually seen with partial tear) vs lateral antebrachial cutaneous nerve entrapment

-Brachialis (deep to biceps; inserts on ulnar tuberosity; tendon surrounded by muscle so not commonly injured; tendonitis/sprain aka “climber’s elbow”)

·        Posterior compartment

-Triceps brachii (broad insertion on prox olecranon; ok to have high T1/T2 signal striated signal at insertion; tendon rupture is least common; may have degeneration if associated olecranon bursitis; dialysis/lupus/HPT predispose to rupture; laxity of tendon ok if elbow fully extended)

-Anconeus (triangular/curvilinear; arises from posterior aspect of lateral epicondyle and inserts laterally on olecranon; helps identify lateral from medial elbow on axial)

·        Medial compartment (more commonly injured than lateral compartment even though lateral epicondylitis more common)

-Common flexor tendon (conjoined tendon insert on medial epicondyle; disruption more common than common extensor tendon; “golfers” or “pitchers” elbow)

-Flexors of wrist/hand (deepest; flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis)

-Palmaris longus

-Pronator teres (most superficial)

·        Lateral compartment

-Common extensor tendon (conjoined tendon inserts on lateral epicondyle)

-Extensors of wrist/hand (extensor carpi radialis brevis=most common culprit in lateral epicondylopathy, extensor digitorum, extensor digiti minimi, and extensor carpi

 ulnaris originate for lateral epicondyle however, extensor carpi radialis longus originates from lower supracondylar ridge of humerus )

         -Supinator (wraps around radial neck)

         -Brachioradialis (big muscle anterolateral; arises from upper supracondylar ridge of humerus)


NERVES (axial T1 and T2)


-Neuropathy (nerve=increased T2 signal, thickened nerve, indistinct fascicles, fluid around nerve; muscle=acute neurogenic edema, late fatty infiltration and muscle atrophy)

·        Ulnar nerve (injury more common than other nerves; located posterior to medial epicondyle)

-Cubital tunnel (floor=post/transverse bundles of ulnar collateral lig; roof=”proximally” by CT retinaculum aka osborne lig extending from olecranon to medial epicondyle but it may be absent/incomplete and “distally” by flexor carpi ulnaris aponeurosis aka arcuate lig)

-Cubital tunnel syndrome=paraesthesia ring and little finger (thickened CT retinaculum; thickened ulnar collateral lig; bone spur at medial epicondyle; anomalous anconeus epitrochlearis muscle replacing CT retinaculum; anomalous lig of spinner; absent CT retinaculum resulting in subluxation/friction; thickened CT retinaculum; pressure from wheelchair or OR table compression; masses)àtravels thru guyon’s canal in wrist

-Look for “surrounding” increased T2 signal with enlarged or flattened or irregular nerve (may have magic angle on PD imaging)

·        Median nerve (not important)

-Best seen on prone imaging; located over brachialis muscle and deep to bicipital aponeurosis of biceps tendonàthen passes btwn ulnar and humeral heads of pronator teresàthen gives rise to anterior interosseous nerve branch (motor only) at inferior margin of pronator teres

-Pronator syndrome (dynamic compression btwn two heads of pronator teres muscle)

-Median neuropathy (pronator syndrome most common; other etiology includes thickened bicipital aponeurosis, biceps tears, radiobicipital bursitis, supracondylar process of humerus)

-Anterior interosseous syndrome (aka Kiloh-Nevin syndrome; rare; anterior interosseous nerve is motor branch of median nerve; cant flex distal joint of thumb/index, look for classic muscle edema of flexor pollicis longus, pronator quadratus, and a part of flexor digitorum profundus)

·        Radial nerve

-Located btwn brachialis and brachioradialis muscle  (anterior to lateral epicondyle); divides at elbow joint near capitellum into superficial radial nerve (sensory; superficial to supinator muscle; follows course of radial artery) and posterior interosseous nerve (motor; penetrates btwn deep and superficial fibers of supinator muscle to course along interosseous membrane); arcade of Frohse is fibrous arch btwn brachialis and brachioradialis seen in 35-50%

-Radial neuropathy (proximal to elbow joint; secondary to trauma, crutches, tourniquet etc; increased signal)

-Radial tunnel syndrome or Posterior interosseous syndrome (aka supinator syndrome or deep radial nerve syndrome; at elbow joint; motor only; secondary to thickened arcade of Frohse, fx/disloc of prox radius, abnormal recurrent vessel along interosseous membrane at elbow joint; increased signal seen w/in posterior compartment muscles w/ edema/fatty atrophy of deep fibers of supinator muscle)





-Loose bodies (axial and sagittal views esp GRE; look for donor site and synovitis; may be secondary to OCD vs acute trauma vs posteromedial olecranon impingement in throwing athletes seen within post olecranon fossa)


-bicipitoradial bursa (BRB)=deep to biceps tendon (r/o radial artery aneurysm) AND interosseous bursa (IOB)=superficial to biceps tendon (both located in AC region on elbow; both communicate w/ each other and can affect median nerve or posterior interosseous branch of radial nerve)

-olecranon bursa (may be seen in Gout)

-Epitrochlear adenopathy (cat-scratch disease; Bartonella henselae)

-Steroid injection for epicondylitis (peritendinous approach); PRP injection (intratendinous approach)





LIGAMENT (thin slice coronal GRE): low to intermediate signal on GRE; consider abnormal if high signal (equal to fluid) or discontinuity/thinning/elongation or increased intercarpal space


INTRINSIC (intercarpal):

-SCAPHOLUNATE (dorsal=dark ”band”, middle=intermediate ”triangular”, volar=intermediate 

“trapezoidal” which actually attaches directly to bone; dorsal and volar more important)

-LUNOTRIQUETRAL (smaller; intermediate signal; assoc with TFCC tears)

EXTRINSIC (radiocarpal)—are intracapsular but extrasynovial; importance unclear!!

-VOLAR (more imp; stronger and thicker; obliquely oriented and striated; both originate from radial styloid; superior RSC=radioscaphocapitate which crosses waist of scaphoid, inferior-lateral and larger RLT= radiolunotriquetral)

               -DORSAL (obliquely oriented from radius to all the bones of prox carpal row; also seen on sag view)


TFCC (SIMILAR TO MENISCUS): best seen on coronal (except for RUL, use sag)


-TFC (biconcave/bowtie disc; attaches to high-signal cartilage of lateral radius; attaches to fovea of ulnar head and to ulnar styloid near UCL; thickness inversely proportional to degree of ulnar variance meaning thinner in pos var and thinner in neg var; assessment like knee meniscus—intrasubs degen=esp central portion with intermediate signal/thinning/ perforation  vs traumatic partial/full thickness tear=prox/distal/radial/central/ulnar aspect vs detached; traumatic tear sequence of worsening severity: tear of TFCàdiscontinuity of ECU sleeveàtear ulnar attachmentàinstability of DRUJàtear lunotriquetral lig;  normally striated ulnar aspect in young patients; tears at vascularized ulnar aspect hard to see and may heal spont; synovitis or synovial proliferation along ulnar prestyloid recess mimic ulnar sided TFC tear; TFC may get torn & trapped in DRUJ)

-RadioUlnar Lig (associated band-like, not biconcave, striated volar/dorsal lig btwn sigmoid notch of radius and ulnar styloid; blends in with TFC; attached to bone, not radial cartilage; imp for DRUJ stability)

-ULNAR COLLATERAL LIG (from ulnar styloid to triquetrum; represents thickening of wrist joint capsule; RCL=radial collateral lig is the counterpart on the other side of wrist from radius to scaphoid)

-ECU TENDON SHEATH Extensor Carpi Ulnaris (located dorsal groove of ulna; best seen on axial; sheath not seen unless tenosynovitis; may sublux/dislocate out of groove medially w/ sheath disruption; may have magic angle near ulnar styloid)

-MENISCAL HOMOLOGUE (triangular thickening of ulnar aspect of capsule; may be absent; attaches to triquetrum or base of 5th MC; prestyloid recess=located inferior to meniscal homologue, around tip of ulnar styloid normally contains fluid)

-Ulnolunate and Ulnotriqueral ligaments (vertically /obliquely anchor TFC)

-Fluid in DRUJ or fluid in pisotriquetral recess is normal (along volar aspect)




-DISTAL RADIUS: sigmoid notch (DRUJ), scaphoid fossa (scaphoid), lunate fossa (lunate), lister tubercle (dorsal)

-REPETITIVE STRESS INJURY (BM edema distal radius at subphyseal involving metaphysis in gymnist; hamate in bicyclist; lunate in martial arts which may be precursor to AVN)

-SCAPHOLUNATE DISSOC (SLAC=prox migration of capitate)

-SCAPHOID FX (rotatory subluxation=scaphoid tilts volar)

-VISI (lunotriquetral disruption; lunate tips volar; SL<30deg) / DISI (scapholunate dissociation; lunate tips dorsal; SL>60deg)

-TYPE II LUNATE (hamate)

-DRUJ (small fluid prox OK; sigmoid notch of radius; look for ulnar subluxation)

-ULNAR NEG (KEINBOCK—lunate AVN may be partial hence, not definite)

-ULNAR POS (ABUTMENT SYN—lunate/ulna cartilage degen, lunate subchondral edema/cyst, TFC tear)

-OS STYLOIDEUM (”carpal boss”, 2nd/3rd MC base dorsal; bursitis, synovial cyst)

-AVN (T1/T2 dark classic; T1 dark but T2 bright is non-specific—possible ischemia vs BM edema vs healing, T1 bright and T2 intermediate is normal; fat signal indicates viability)

-RA (erosions, proliferative enhancing synovitis, ”pannus”, tenosynovitis, bursitis, ST nodule aka rheumatoid nodule, numerous rice bodies)

-INTRAOSSEOUS LESION (ddx: bone cyst, geode, intraosseous ganglion, erosion)


TENDON: best seen on axial


-Small fluid in tendon sheath may be normal if non-circumferential

-TENOSYNOVITIS= circumferential fluid within sleeve vs synovial proliferation, fusiform swelling/enlargement of tendon over longer length with abnormal signal within tendon aka edema

-INTERSTITIAL TEAR of tendon=difficult to tell from tenosynovitis but are sharply marginated signal within tendon

-TENDINOPATHY=intermediate signal within tendon


-6 EXTENSOR COMPARTMENTS (located dorsally; extensor retinaculum w/ fascial septations separating compartments; II and III separated by Lister’s tubercle; ECU in 6th compartment along ulnar groove may have magic angle artifact; ECU may be subluxed/dislocated; small fluid in tendon sheath OK unless completely surrounds the tendon)

-9 FLEXORS TENDONS (pass thru carpal tunnel)—don’t need to know their names!!

-DEQUERVAIN’S (entrapment/tenosynovitis of 1st compartment along radial styloid; varied appearance on MRI—not always high T2 signal; acute=may be tendon fusiform thickened/internal signal/surrounding signal/loss of adj fat; chronic=low to intermediate T2 signal with fibrous adhesions in sleeve can be painful; idiopathic vs pregnancy vs manual labor; tx=steroid vs surgical decompression)

-DISTAL INTERSECTION syndrome (tenosynovitis of 2nd and 3rd compartments distal to Lister’s tubercle where the tendon sheaths are connected by foramen)




-Trigger finger (repetitive trauma of A1 pulley near MCP jt; flexor stenosing tenosynovitis; sensation of finger catching; steroid inj helps)

-Flexor tendon tear (Flexor Dig Profundus FDP vs Flexor Dig Superficialis FDS; identify site of tear and degree of prox retraction; tendon rupture is rare)

-Flexor pulley system injury (fibro-osseous canal; 5 annular pulleys + 3 cruciform pulleys; numbered from prox to distal; A1 thru A5 with odd number at joint while even number along phalanx; most commonly injured A2àthen A3àthen A4; in rock climber usually tear A2 and A4 with “bowstringing” on sag àcorrelate on axial to see what part of pulley is injured=radial vs ulnar aspect or apex)

-Extensor tendon tear (EDC has central and medial/lateral slips; sagittal bands stabilizes it at MCP and retinacular lig stabilizes it at middle phalanx; retinacular lig may be torn on one side with subluxation of tendon)

-MCP collateral lig injury (usually at base of thumb=gamekeeper’s see below; UCL vs RCL; +/-avulsion fragment)

-Volar plate (injured during hyper-extension)


NERVE: best seen on axial


-MEDIAN NERVE IN CT (flexor retinaculum is 2.5-3.5mm thick and bows slightly out towards palm; intermediate signal oval median nerve on the radial and volar aspect; normally very little fat in CT except dorsal aspect; evaluate median nerve at DRUJ prior to CTàat pisiform in prox CTàat hook of hamate in distal CT where MN most constricted, may be flat, and closely opposed to flexor tendons; size of MN is maintained or slightly decreases distally; narrowest portion of carpal tunnel is distally at level of palmar-oriented prominence of capitate ~10mm AP width)

-CARPAL TUNNEL SYNDROME (4 findings=focal or segmental swelling/enlargement by 50% aka pseudoneuroma at level of pisiform + focal flattening/angulation of MN at level of hamate + increased MN T2 signal + increased palmar bowing of flexor retinaculum ratio >15% at level of hamate)—other etiologies=tenosynovitis of flexor tendons, ganglion cyst

-Failed CTS surgery (residual intact retinaculum, perineuronal fibrotic scarring, MN neuroma)

-Fibrolipomatous hamartoma of MN (stippled nerve fascicles surrounded by fat, may be assoc with macrodystrophia lipomatosa) 

-ULNAR NERVE IN GUYON’S CANAL (ulnar aspect; contains nerve/artery/vein only; nerve is medial to ulnar artery; floor of tunnel=flexor retinaculum and hypothenar muscles; roof of tunnel=volar carpal lig, palmaris brevis muscle; in canal, ulnar nerve divides into superficial sensory and deep motor branches; etiologies include ganglia, hook hamate fx, pisiform-hamate coalition)—r/o ulnar artery aneurysm


NERVES: best seen on axial


-MEDIAN NERVE IN CT (flexor retinaculum is 2.5-3.5mm thick and bows slightly out towards palm; intermediate signal oval median nerve on the radial and volar aspect; normally very little fat in CT except dorsal aspect; evaluate median nerve at DRUJ prior to CTàat pisiform in prox CTàat hook of hamate in distal CT where MN most constricted, may be flat, and closely opposed to flexor tendons; size of MN is maintained or slightly decreases distally; narrowest portion of carpal tunnel is distally at level of palmar-oriented prominence of capitate ~10mm AP width)

-Carpal tunnel syndrome (4 findings=focal or segmental swelling/enlargement by 50% aka pseudoneuroma at level of pisiform + focal flattening/angulation of MN at level of hamate + increased MN T2 signal + increased palmar bowing of flexor retinaculum ratio >15% at level of hamate)—other etiologies=tenosynovitis of flexor tendons, ganglion cyst

-Failed CTS surgery (residual intact retinaculum, perineuronal fibrotic scarring, MN neuroma)

-Fibrolipomatous hamartoma of MN (stippled nerve fascicles surrounded by fat, may be assoc with macrodystrophia lipomatosa) 

-ULNAR NERVE IN GUYON’S CANAL (ulnar aspect; contains nerve/artery/vein only; nerve is medial to ulnar artery; floor of tunnel=flexor retinaculum and hypothenar muscles; roof of tunnel=volar carpal lig, palmaris brevis muscle; in canal, ulnar nerve divides into superficial sensory and deep motor branches; etiologies include ganglia, hook hamate fx, pisiform-hamate coalition)—r/o ulnar artery aneurysm




-EFFUSION (fluid within DRUJ can be normal)

-INTRAOSSEOUS GANGLION (RADIAL ASPECT OF LUNATE)—may enhance esp if not contiguous with joint

-GANGLION CYST (dorsal scapholunate; volar pisotriquetral; may originate w/in scapholunate lig & erode into radial aspect of lunate; multiseptate T1 dark and T2 bright; may be T1 bright due to high protein content; Gad to exclude mxyoid tumor)—r/o ulnar artery aneurysm

-SYNOVIAL CYST (arising from pisotriquetral jt—synovial recess vs cyst if >1cm; cyst may be symp; like bakers cyst)

-EROSIONS (ULNAR STYLOID AND MCPs)—look for enhancement and assoc synovitis; confirm on plain film

-GCT TENDON SHEATH (VOLAR FLEXOR TENDON; T1/T2 DARK; scallops bone surface; may have heterogenous enhancement; ddx=gouty tophus, amyloid deposit)

-MASSES=schwanoma, neurofibroms, fibromatosis (palmar), glomus tumor (distal phalanx)

-Gamekeeper’s thumb (vertically oriented ulnar collateral lig UCL at MCP; adductor aponeurosis is thin band also vertically oriented but normally located superficial to UCL; Stener lesion=torn intermediate signal UCL retracted prox and displaced superficial to aponeurosis, “yoyo on a string”; look for avulsion frag, BM edema, chondral injury, and adductor pollicis muscle edema)


VESSELS: -Hypothenar hammer syn (repetitive trauma to heel of palmàspasm/thrombosis/aneurysm ulnar a.àdigital ischemia)









Bones:                             scout, cor T1, cor PD FS

FAI:                                  axial T1 (angled)

Capsule/cartilage:           cor PD FS (angled), sag PD FS

Labrum:                           cor PD FS (angled), axial T1 FS and PD FS

                                         radial sag PD (parallel to neck)+ axial scout (place crosshair)

                                         sag PD FS (not as useful)

Muscles/Tendons:           axial T1 FS, cor PD FS, and any T1 without FS


OSSEOUS STRUCTURES (for hip imaging, axial and coronal are the most important)


-Acetabulum (bony rim and labrum absent inferiorly at “acet notch” covered by transverse lig; “acet fossa” is devoid of cartilage 

     and filled w/ fibrofatty tissue & synovium)

-acetabular dysplasia; protusio (when femoral head projects medial to ilioischial line); retroversion (figure of 8; anterior acet is more lateral than post acet)

-post disloc (avulsion of post-acet; labral and chondral injuries +/- entrapment; disruption of iliofemoral lig (ant); hemarthrosis; sciatic nerve injury; risk=AVN)

-Femur (lot of red marrow in femur/pelvis which has int signal, higher than muscle; fatty marrow epiphysis & trochanters; marrow       conversion: epiàdiaàmetaphysis)

     -small amount of red marrow in subchondral femur head epi is normal; diffuse red marrow seen with anemia or chronic      

     illness; marrow packing or infiltrative d/o

     -femoral neck 115-140deg with respect to femoral shaft

     -head/neck (fovea centralis does not have articular cartilage but contains low T1/T2 lig teres & pulvinar aka fibrofatty tissueàlig 


     inserts into transverse lig)

     -trochanters (enthesophytes)


-Sacrum (insuff fx parallels SI joint & may cross midline if bilateral aka “Honda sign”), Ilium (supracetabular “raised eyebrow” 

  insuff fx)

-Ischium (esp ischial tuberosity)      

-Pubic rami and symphysis  

-SI joints (true synovial joint ant-inf half w/ thinner cartilage on iliac side where DJD begins first): bilat symm=ank spond & IBD


-Red marrow (usually symmetrically involves metaphysis; conversion to yellow from appendicularàaxial and epiàdiaàmetaphysis; small amount of red marrow in subchondral region OK but can mimic AVN; signal > than muscle on T1 o/w think infiltrative marrow ddx=tumor, OM, edema/trauma, marrow-packing d/o)

-Fracture (T1 coronal +/- STIR, axial T2)—stress fx=sclerotic T1/T2 w/ T2 edema compressive>tensile neck; fatigue fx= may lack sclerosis)

-Stress injury of tibia (gradeI=periosteal edema, gradeII=also endosteal/BM edema on T2, gradeIII=also abnl BM signal on T1, gradeIV=fx line visible)

-AVN early=diffuse then focal edema (can mimic TOH)àserpentine low T1 signal surrounding fatty center (ant-sup head) sharp inner line and ill-defined outer margin due to gray edemaàdouble line sign T2 (hi signal granulation tissue paralleling along inside margin of dark sclerotic band)àlate=sclerosis/collapse (subchondral fx and epiphyseal collapse); mimic=gray signal subchondral normal red marrow; “ASEPTIC” anemia (sickle-cell), steroids, ethanol, pancreatitis, trauma, idiopathic, CVD, XRT, LCP, Gaucher’s

-TOH=preg women 3rd tri < middle-aged men 40-50yo M>F 3:1 no trauma, spont res in 6-8mos, hi T2 from head to intertrochanteric region (unilat), no subchondral low T2 signal (<4mm thick and <1.25cm long c/w irreversible AVN), acetabulum uninvolved, may have effusion, MR +ve 48hrs after pain onset; penia on xray within 4wks (ddx=early AVN or insuff fx or osteoid osteoma)

-Lig teres tear (normally homogen low T1/T2; post-traumatic partial/complete tear vs degeneration=hypertrophied lig can be assoc w/ CPPD--osseous erosion/irreg of fovea)

-Inflamm arthritis (septic and aspectic inflamm arthritis appear similar)—thickened enhancing synovium, bone marrow edema, effusion, erosions

-Septic hip (effusion + synovitis; synovial thickening and enhancement; BM edema both sides of joint; mono-articular; aspiration fluid PMN>80k is diagnostic criteria)

-Sickle cell (OM vs Infarct; cannot differentiate on MR; consider In-WBC + Tc-SC)



FAI (pain w/ flexion/internal rot; assoc w/ ant-sup labral tear; bony frag or os acetabulae at sup-lat acet rim; fibrocystic lesion or synovial herniation pit)

--PINCER=acet overcoverage due to coxa profunda or acetabular protusio resulting in retroversion “crossover” sign of ant acet c/w pincer-type morphology assoc with FAI + anterior-superior labral tear (perpendicular to articular surface) + post-inf acet countercoup chondral injury

--CAM=femoral head-neck offset with anterior-superior (seen best on axial-oblique) vs lateral (seen best on AP or radial sequences) dysplastic/aspherical bump (“pistol grip” deformity); alpha angle>55 on axial-oblique images (prescribed parallel to long axis of femoral neck); head-neck offset <10mm; labral initially sparedàthen ALAD=acetabulolabral articular disruption (labrum separated from cartilage at chondralabral jct); may have associated anterior-superior cartilage tear (deep / superficial / flap tear) vs delamination (inverted oreo cookie sign with contrast or fluid undermining articular cartilage)

--Herniation pit (always abnl; in-growth of fibrocartilaginous tissue thru cortical defect; aka fibrocystic lesion; ant-sup-lat at head/neck jc; can be uni/bilateral)

--also look for BM edema, subchondral cystic changes, intraosseous ganglion, synovitis (obscuration of normal sulcus btwn sup labrum and capsule may be an early sign), and capsular thickening (hypertrophy of iliofemoral lig)




Tendonitis/Tendinopthy; partial/full-thickness tear; avulsion; HADD (calcific tendonitis); myotendinous strain; stress injury

-Anterior: flex (quadriceps=rectus femoris + vastus lateralis/intermedius/medalis; sartorius)

-Medial: adduct (GPA=gracilis, pectineus, adductor longus/brevis/magnus) ßGROIN PULL

-Lateral: abduct (tensor fascia lata, gluteus max/med/min)ßGR TROCHANTERIC PAIN SYNDROME (glut med/min tendinopathy/tear > avulsion of gr torchanter)

-Posterior: extend (hamstrings= biceps femoris + semimemb + semitend) ßHAMSTRING INJURY tear (usually SM) vs ischial tuberosity avulsion (usually of conjoint tendon of BF/ST)

-External rotators: (piriformis, quadratus femoris, GOGO’s=gemellus sup/inf and obturator int/ext) ßPIRIFORMIS SYNDROME (sciatic nerve neuropathy; mimics radiculopathy)—sciatic nerve located ant or may split thru piriformis and exits via greater sciatic notch




AIISàrectus femoris

Iliac alaàGluteal muscle origin

Superior pubic ramusàpectineus muscle

Inferior pubic ramusàadductor longus

Pubic symphysisàadductor brevis and gracilis

Ischial ramusàorigin of other adductors

Ischial tuberosityàhamstring origin (superolateral=semimembranosis; inferomedial=conjoint tendon of semitendinosis and long head biceps femoris; BF muscle located lateral, SM inbetween, ST medially; BF and ST come together as conjoint tendon); also insertion of sacrotuberous lig; note: adductor magnus inserts slong inferior aspect of ischial tuberosity

Gr trochanterà”GOP” Glut med (lateral and superoposterior), Glut min (anterior), Obturator internus, Piriformis insertion, Bursa (post)

Ls trochanteràIliopsoas insertion

Gluteal tuberosity of prox femuràGlut maximus insertion

Linea aspera (femoral diaphysis)àinsertion on many muscles


-Muscle strain:

-strain (edema at myotendinous junction vs less commonly peripheral edema in epimysial strain' commonly involves hamstring, rectus femoris, medial gastroc, and biceps brachii); laceration (knife); contusion (localized edema with associated ST and BM edema); tear (discontinuity); hemorrhage (can mimic mass so give gad on f/u exam); compartment syndrome (edematous muscle compartment with fascial edema)

-GradeI (pain)=microscopic at musculotendinous jct w/ T2 feathery edema w/ preserved morphology; GradeII (pain/weakness)=partial thickness tear w/ discrete T1 bright intramuscular hematoma or fluid collection (tearing of up to <50% of muscle fibers); GradeIII (pain/weakness/loss of fxn)=complete tear “bull’s eye” appearance +/- retraction

-Longer the length of muscle involvement, longer it would take to resolve; more edema/fluid means higher grade; complete tendon or myotendinous tear is Grade III; chronic tear associated with thickened tendon and peritendinous or diffuse muscle atrophy.

-Muscle edema ddx=muscle injury (strain/tear); myositis (increased T2 signal; may be subtle if autoimmune; more obvious and more enhancement if infectious); inflammatory myopathy; DOMS; acute/subacute denervation

-Muscle denervation= acute (increased muscle volume, T2 bright, no fatty infiltration, +muscle enhancement), subacute (normal muscle volume, T2 bright, early fatty infiltration, +muscle enhancement), chronic (decreased muscle volume, no longer T2 bright, increased muscle infiltration, no muscle enhancement)

-Fascitis (inflammation/fluid/edema tracks along deep fascial planes; +/- assoc myositis; +/-abscess/microabacesses)

-Nec Fascitis (clinical diagnosis; destruction & necrosis of subcutaneous and deep fascial tissues with dull gray appearance of fascial edema; +/-myonecrosis; +/-abscess/microabscesses; look for vascular thrombosis; late=gas gangrene; spreads rapidly; Gad not necessary but useful to identify abscess but can underestimate extent of necrosis; typeI=polymicrobial 90% vs typeII=flesh-eating 10%)


-Snapping hip (multiple causes including slipping of iliopsoas tendon over iliopectineal eminence w/ hip flexion/extension)

-Athletic pubalgia (rectus abdominus, pectineus, adductor longus, and levator ani insert at pubic symphysis; tear of rectus abdominis leads to compartment syndrome in region of adductor muscle near sup margin of inf pubis; marrow edema in pubic symphysis and nearby portion of pubic rami and adj muscle edema esp adductors along with tendon tears and even hematoma)

-Osteitis pubis (multiparous women; marrow edema and irreg of pubic symphysis w/ fluid within cartilaginous joint ; may have AP or sup-inf joint incongruity)

-Gluteal tear (aka rotator cuff of hip) from greater trochanter which has 4 facets=“anterior” (GlutMin), “lateral” (GlutMed—lateral tendons), “posterior” (trochanteric bursa), “superoposterior” (GlutMed—main tendon); partial/complete tear, avulsion of gr trochanter, glut muscle atrophy

-Abnl muscle signal DDX: bursitis, strain/tear (usually at myotendinous jct), DOMS, contusion/hematoma, myositis, acute denervation (<2wks-1year)

-Intramuscular tumors DDX: hemangioma (contains fat, calc, serpiginous vessels), lipoma, myxoma (mimics cyst but enhances), sarcoma (no surrounding edema), mets (has surrounding edema), lymphoma, neurofibroma (“target”), desmoid & MFH(=low T1 and low/int T2), hematoma, myositis ossificans


LABRUM/CARTILAGE (dedicated hip arthrogram)



-post-sup labrum is thicker; labrum usually triangular but may be non-triangular (rounded/flat) in older pts         

->90% are anterior or antsup tears (there are no normal variants here!); clockface on sag plane (ant is 3’oclock)   

-base vs periphery of labrum     

-Resnick classification: longitudinal vertical, longitudinal horiz, radial, complex, labral detachment, acetabulolabral articular destruction (ALAD)

-Others use: degeneration (common>50yo) vs tear (linear/heterogenous signal; deformed/distorted contour) vs detached (partial/complete +/-displacement; contrast interposed at acetabular-labral jct or interface)


-normal labral variants more common in lower quadrant; no normal variant within ant to sup labrum

-post-inf sublabral sulcus on axial

-perilabral recess btwn labrum and capsule (small ant and post; larger superiorly)

-?ant-inf sublabral sulcus  (linear-cleft, only partial separation, no perilabral abnl)

-labro-ligamentous sulcus/recess btwn labrum and transverse lig anteriorly and posteriorly  on cor/sag; anterior labrum pitfall is adj iliopsoas tendon on axial

-cartilage undercutting

-Paralabral/para-articular cyst—may be intra-osseous subchondral (within acetabulum)



-Stellate crease or supra-acetabular fossa (focal notch in superior acet 12’oclock devoid of cartilage w/o BM edema in young pts; may contain plica or fibrous cord)

-capsule inserts directly at base of labrum anteriorly and posteriorly with a small “perilabral recess”; larger “perilabral recess” seen superiorly

-capsule inserts anteriorly along intertrochanteric line and posteriorly halfway down femoral neck

-capsule reinforced by 3 longitudinal capsular ligs: ANT: Iliofemoral=strongest (Y-shaped=medial and lateral bands) + Pubofemoral (hiatus btwn iliofem and pubofem allow comm. w/ iliopsoas bursa in 15%), POST: Ischiofemoral (sup and inf bands)

-circularly oriented fibers known Zona Orbicularis encircles the capsule at base of femoral neck (forms a collar)


Cartilage (“acet fossa” not covered with cartilage): thinning, fissuring, delamination, partial/full thickness defect, chondral flap seen w/ full-thickness tears; PINCER=assoc w/ countercoup post-inf cartilage degen; CAM=assoc w/ ant-sup cartilage degen





-Sciatic nerve=tibial nerve+common peroneal nerve (immed post to post column of acet and lat to ischial tuberosity hamstring insertion; ant to piriformis thru greater sciatic foramen; located btwn quadratus femoris muscle ant and glut max post; normal intermediate stippled signal surrounded by fat; compressive neuropathy or fibrolipomatous hamartoma)

-Piriformis syndrome (piriformis muscle hypertrophy vs inflammation vs anatomic variation leads to compression on sciatic nerve; seen as abnl signal within piriformis muscle; 85% sciatic nerve anterior to piriformis muscle; 12% TN and CPN are split by piriformis with CPN thru muscle; 3% CPN posterior to piriformis with TN thru muscle; 1% sciatic nerve thru muscle)

-Femoral nerve (inguinal canal; etiology include inguinal hernia, iliopsoas bursitis, psoas abcess, aneurysm, etc)

-Obturator nerve (obturator canal; etiology include obturator hernia, osteitis pubis, paralabral cyst)

-Lateral femoral cutaneous nerve (L2/L3; entrapment=”meralgia perasthestica” pain/burning/numbness prox lateral thigh; etiology=neuroma vs compression at ASIS near attachment of inguinal ligament overlying iliacus muscle)


Bursa (intrabursal steroid injection)

-iliopsoas bursitis=largest bursa in body; 15% comm. w/ joint; distended in OA/RA/infx; anterior to hip & med to iliopsoas tendon (more lat than paralabral cyst); “hourglass” appearance on coronal; adj to fem A/N/V; may be painful/palpable (mimics mass; gad shows peripheral enhancement)

-greater trochanteric bursitis (mimics gluteal tear in pts w/ lateral hip pain)=3 bursa (“trochnateric” bursa along posterior facet and GluMed & VasLat; “subgluteal medius” bursa btwn GlutMed and lateral facet; “subgluteus minimus” and anterior facet)-- bursa fluid, reactive edema of gr trochanter, and adjacent inflamm changes (survey overlying IT band/tensor fascia lata to r/o “trochanteric friction syndrome”)


-Morel Lavallee (closed degloving injury; sudden violent stress shear; subq hemolymphatic mass along anterolat prox thigh; capsulated)

-PVNS (monoarticular; synovial proliferation w/ hemosiderin tells it from synovial chondromatosis or amyloidosis; pressure erosions)

-Myositis ossificans (rim=low signal calc; center=high signal fatty marrow)



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