Osteochondritis dissecans (OCD) is the end result of the aseptic separation of an osteochondral fragment with the gradual fragmentation of the articular surface. It is often associated with intraarticular loose bodies.
Onset is between childhood and middle age, with the majority of patients being between 10 and 40 years of age, with approximately a 2:1 male to female ratio 3.
Symptoms are variable and range from asymptomatic to significant pain and locking (suggesting loose body formation). Joint effusions and synovitis are often present.
The exact aetiology is uncertain, with the majority of cases thought to be the result of trauma 4. In up to 40% of cases, patients give a history of trauma as the inciting event 3. Other postulated causes include 4:
- avascular necrosis (AVN)
- fat emboli
- familial dysplasia
Many joints can be affected, but typical locations include:
- femoral condyles: most common site accounting for approximately 75% of all cases: see osteochondritis dissecans of the knee
- patella may also be involved
- ankle (talus): see osteochondritis dissecans of the ankle
- elbow (capitellum): see osteochondritis dissecans of the elbow
Plain radiographs should be the first step in the evaluation of knee pain, however, unless advanced changes are present and / or a meticulous technique employed, early findings of osteochondritis dissecans may be occult. The intercondylar "notch" view is very helpful.
Early findings include subtle flattening or indistinct radiolucency about the cortical surface. As the process progresses, more pronounced contour abnormalities, fragmentation and density changes (both lucency and sclerosis) become evident. If an osteochondral fragment becomes unstable and displaced, then donor site and intra-articular fragment may be seen.
CT has the advantage of sectional imaging through the joint and multiplanar reformats. Findings are similar to those seen on plain film.
MRI is the test of choice, with high sensitivity (92%) and specificity (90%) 4 in the detection of separation of the osteochondral fragment. This is essential in determining management.
- variable signal overall with intermediate to low signal adjacent to fragment and variable fragment signal
- high signal line demarcating fragment from bone usually indicates an unstable lesion however false positives can result from oedema 6
- low signal loose bodies, outlined by high signal fluid
- donor defect filled with high signal fluid
- high signal subchondral cysts
Treatment and prognosis
Spontaneous healing is usual unless there is an unstable fragment, and treatment revolves around rest and immobilisation for up to a year 5.
When the fragment is unstable or displaced, without treatment patients are susceptible to premature secondary osteoarthritis. Numerous surgical approaches have been tried, including drilling, bone grafting, replacement of bone fragment and pinning 5.
When surgery is performed, the results in most cases are only "fair". 35-70% of patients achieve a "good to excellent" clinical outcome 3 but even in these cases, the majority develop osteoarthritis.
History and etymology
It was first described by the German surgeon Franz Konig in 1888.
- normal irregular distal femoral epiphyseal ossification
- avascular necrosis
- osteochondral impaction fracture
- stress/insufficiency fracture
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- 3. Michael JW, Wurth A, Eysel P et-al. Long-term results after operative treatment of osteochondritis dissecans of the knee joint-30 year results. Int Orthop. 2008;32 (2): 217-21. doi:10.1007/s00264-006-0292-7 - Free text at pubmed - Pubmed citation
- 4. Maeurer J. Imaging strategies for the knee. Thieme Publishing Group. (2006) ISBN:3131405619. Read it at Google Books - Find it at Amazon
- 5. Sailors ME. Recognition and Treatment of Osteochondritis Dissecans of the Femoral Condyles. J Athl Train. 1994;29 (4): 302-306. Free text at pubmed - Pubmed citation
- 6. De smet AA, Fisher DR, Graf BK et-al. Osteochondritis dissecans of the knee: value of MR imaging in determining lesion stability and the presence of articular cartilage defects. AJR Am J Roentgenol. 1990;155 (3): 549-53. AJR Am J Roentgenol (abstract) - Pubmed citation