Osteochondritis dissecans (OCD) is a joint condition characterized by the interruption of the blood supply to a section of bone and cartilage. This leads to the detachment of the bone and cartilage from its surrounding area, potentially allowing it to move freely within the joint space. The most commonly affected joints are the knee, elbow, and ankle.

It generally affects children and young adults. OCD may progress to degenerative changes if untreated.

Aetiology

The exact cause of OCD remains uncertain, but it is believed to result from a combination of mechanical and biological factors. Potential aetiological factors include:

• Repetitive trauma or overuse of the joint
• Genetic predisposition
• Variations in bone growth or maturation
• Poor blood supply to the subchondral bone

PC

Patients typically present with a subacute onset of:

• Knee pain and swelling, typically after exercise
• Knee catching, locking and/or giving way: more constant and severe symptoms are associated with the presence of loose bodies
• Feeling a painful 'clunk' when flexing or extending the knee - indicating the involvement of the lateral femoral condyle

Signs:

• Joint effusion
• Tenderness on palpation of the articular cartilage of the medial femoral condyle, when the knee is flexed