Osteochondritis dissecans

In osteochondritis dissecans (OCD) a small segment of articular cartilage and subjacent bone may separate - dissect - as an avascular segment.

• in majority the cause is idiopathic, other proposed etiological factors include trauma (either macrotrauma or repeated minor trauma), vascular insufficiencies (1)
• commonly seen in the knee, but can affect other joints as well e.g. - elbow, shoulder, ankle and hip (1).
• is usually unilateral, but may present with bilateral disease (1)
• characteristically, this condition affects patients between the ages of 13 to 21 years (1)
• the lateral aspect of the medial femoral condyle is the affected site in 70 – 80% of OCD lesions (1).

The patient presents with vague, poorly localised intermittent pain, morning stiffness, swelling and joint effusion of the affected joint. The necrotic fragment may become detached and result in the joint 'locking', ‘catching’ or 'giving way' (1).

On examination:

• there may be quadricep atrophy, focal bony tenderness, a mild knee effusion, palpable loose body and knee extension block (2,3)
• Wilson's signs may be positive - the knee flexed to 90 degrees with the tibia rotated medially while extending the knee, the test is positive when the pain occurs at approximately 30 degrees of flexion and relieved by lateral rotation of the patella (2)

In suspected cases of osteochondritis dissecans, order X-rays of both knees.

• may demonstrate the osteochondral lesion or a loose body in the knee joint (3)
• specific views such as weight bearing anteroposterior and posteroanterior tunnel views, lateral and tunnel views might be necessary (1).

Treatment is dependent upon the position of the fragment.

• if the fragment is in position (stable lesions) then the treatment consists of conservative methods (e.g.- weight-relief and restriction of activity) . In a child there may be complete healing, although this may take up to 2 years. Drilling through the fragment to try to revascularise it in situ has been attempted.
• if the fragment becomes detached and symptomatic then it should be pinned or removed.

Osteochondritis dissecans predisposes the individual to osteoarthritis.

Reference:

• (1) Detterline AJ et al.Evaluation and treatment of osteochondritis dissecans lesions of the knee. J Knee Surg. 2008;21(2):106-15.
• (2) Houghton KM. Review for the generalist: evaluation of anterior knee pain. Pediatr Rheumatol Online J. 2007;5:8.
• (3) Calmbach WL, Hutchens M. Evaluation of patients presenting with knee pain: Part II. Differential diagnosis. Am Fam Physician. 2003;68(5):917-22