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Osteochondritis dissecans

'Osteo' means 'bone'. 'Chond' means cartilage. 'Itis' means 'inflammation'. Osteochondritis means inflammation of bone and joint cartilage. Dissecans means breaking away.

This is a very particular form of chondral defect, but one in which there is less often a story of an injury. It is a condition usually of physically active teenage boys, although it does also occur in girls and in adults. It is relatively rare but very upsetting when it occurs. The other knee is sometimes also affected by the same condition.

The condition causes pain and there may also be the symptoms of a loose body - catching and locking in the joint. It is usually the medial femoral condyle which is affected (the inner rounded end of the thigh bone).

Although there are loads of theories, there has not been any definitive answer from the medics as to why this condition occurs.

The real difficulty is that the bone underneath the joint cartilage dies, and then there is no nourishment to the cartilage itself. The cartilage piece becomes unstable and suddenly breaks off in a chunk and falls into the joint as a loose body. To treat it effectively it is important to make the diagnosis before the cartilage bit breaks off, but the clinical signs are so very subtle at this stage and inexperienced doctors may not specifically look for them. In early stages the bone may be drilled to encourage blood vessels to grow back to the cartilage. In later stages a surgeon may use any of the joint surface treatments (see that section).