Osteochondrosis Dissecans

= OSTEOCHONDRITIS DISSECANS = OSTEOCHONDRAL FRACTURE

= fragmentation + possible separation of a portion of the articular surface

Etiology:

subchondral fatigue fracture as a result of shearing, rotatory / tangentially aligned impaction forces / repetitive microtrauma
? autosomal dominant trait associated with short stature, endocrine dysfunction, Scheuermann disease, Osgood-Schlatter disease, tibia vara, carpal tunnel syndrome

Age: adolescence; M >F

Location:

knee: medial (in 10% lateral) femoral condyle close to fossa intercondylaris; bilateral in 20–30%
humeral head
capitellum of elbow
talus

purely cartilaginous fragment unrecognized on plain film
fracture line parallels joint surface
mouse = osteochondrotic fragment
Location: posterior region of knee joint, olecranon fossa, axillary / subscapular recess of glenohumeral joint
mouse bed = sclerosed pit in articular surface
soft-tissue swelling, joint effusion

MR:

focus of abnormal signal in subarticular marrow
defect in overlying cartilage
loose bodies of heterogeneous low-SI in coronoid and olecranon fossa outlined by hyperintense joint fluid on T2WI

DDx: spontaneous osteonecrosis, neuroarthropathy, degenerative joint disease, synovial osteochondromatosis

Juvenile Osteochondritis Dissecans of Knee

= disease manifestation before physeal closure

Etiology: repetitive trauma

Age: 10–15 years; M÷F= 3÷1 to 4÷1

pain, clicking / catching of joint, loss of function ← intra-articular loose bodies

Site:

medial femoral condyle: posterolateral aspect (51%), weight-bearing portion (19%)
lateral femoral condyle: medial aspect (7%)

signs of lesion instability (= high-grade lesion):
line of fluid signal intensity on T2WI between fragment + parent bone surrounded by low-intensity rim
multiple / >5 mm cysts near lesion
fracture in articular cartilage
fluid-filled osteochondritis dissecans lesion

Osteochondritis Dissecans of Capitellum

Age: adolescent boys 13–16 years of age

Cause: overhead throwing activity / gymnastics

Outline