An unusual cause of knee pain is that of osteochondritis dissecans (OCD). When present, OCD lesions usually become symptomatic during a child’s development. The lesion, which has multiple etiologies, has as a final common pathway the loss of blood supply to a small portion of the bone. That bone becomes separated from the rest of the bone surrounding it, and the bone, with its cartilage cap, becomes loose. This can be thought of as a fragment within a crater. As the fragment becomes loose or breaks off, the symptoms escalate and direct patients to a physician’s office for both diagnosis and treatment. OCD lesions most commonly occur on the medial condyle of the femur, although they can be seen both on the lateral side of the knee and within the patellofemoral joint.
Most OCD lesions occur for unknown reasons. Some believe that the lesion is genetically determined and occurs no matter what the activity level or age of the patient is. Other theories include repetitive trauma or specific trauma to the knee at a young, susceptible age. These types of injuries often go unnoticed when they occur and are recalled only after close questioning of a patient's past.
- Aching pain, not always made worse with activity.
- Mild swelling.
- Clicking and or locking as the piece becomes loose and as it becomes a free fragment.
Treatment of OCD lesions is dictated by the extent of the lesion and the age of the patient at the time of diagnosis. Younger patients with minimal discomfort can be treated with rest and a period of non-weight bearing to allow the bony fragment to heal into its anatomic location.
Alternative Treatment Options
If the fragment is large and/or the patient is older, surgical treatment is often recommended. Surgical treatment is directed first at trying to save the fragment. If a large piece of bone is present, then use of a screw or pin can secure the fragment into its anatomic location and bony healing allowed to occur. However, if the fragment is not large or if it is loose and displaced out of its normal site, then it is usually necessary to remove the fragment entirely and treat the defect as would be done in traumatically caused cases of a chondral (cartilage) defect.