Osteochondritis Dissecans is a painful joint condition, characterised by death of a small area of the joint surface of the bone that may separate from the rest of the bone and dislodge into the joint space. It is a rare disease usually affecting adolescents (age 9-18), especially those involved in active sports.
The surface of a bone in a moveable joint is covered with articular cartilage, which acts as a protective cap, preventing damage to the underlying bone due to the friction created by sliding of bones over one another during joint movement. The part of the bone underlying the articular cartilage is Subchondral bone. It supports the overlying cartilage, providing adequate cushioning as well as maintaining the shape of the joint surface.
In osteochondritis dissecans, the problem starts with the interruption of blood supply to the subchondral bone. The resulting ischemia damages the bone as well as the adjacent articular cartilage, which then sloughs off the bone and may get dislodged into the joint space, causing symptoms.
Although the name “osteochondritis” literally means “inflammation of bone (osteo) and cartilage (khondro)”, it is now known that the disease does not result from inflammation, rather inflammation is secondary to the lesion. The actual cause of the problem is still unclear. Mostly repeated minor trauma causing micro fractures and impairing the blood supply is considered to be the culprit. Nevertheless, genetic predisposition, growth disturbances and hormonal influences are also suspected to be involved.
The knee is the joint most commonly affected; other synovial (freely movable) joints such as the shoulders, elbows, ankles, etc., may also be involved.
In the initial stages, the symptoms associated with osteochondritis dessecans are the same as those seen in other joint conditions including, sprains, arthritis, bone cysts and so on, and are not therefore conclusive of the diagnosis. X-rays, MRI or CT scan are important aids in diagnosis. MRI is a great way to discern any loose fragments, as well as to explore the extent of damage to the joint, helping in staging the disease progress.
Stage I: thickening of the articular cartilage (stable)
Moreover, Technetium 99m bone scans provide information regarding the blood flow and its uptake by the bone, two important factors for proper healing of any lesion.
The treatment plan is dictated by the progressive stage of the disease. If the lesion is stable, conservative approach is usually adopted, while unstable lesions do not heal without surgical intervention.
Adolescents have better prognosis as their bones are still growing. Conservative treatment works well for teenagers having small, stable lesions. The main aim is to prevent stress and further trauma and provide a healing environment to the damaged tissues.
The treatment includes:
- Avoiding weight-bearing or stressful activities
- immobilising the joint with the help of braces or crutches for about four to six weeks
- Later on, physiotherapy is employed to improve the range of motion of the joint and to strengthen the adjacent muscles for a better control of the joint movement.
- NSAIDs for pain control.
The patient is reassessed after three months for radiographic evidence of healing. In the absence of healing, surgery is advised.
For adults as well as for children that have unstable lesions or stable lesions that have not responded to conservative treatment, surgery is recommended.
The surgical procedure varies with the extent of the damage and usually involves an arthroscopic approach (visualising and operating in the joint space using a small scope and special instruments, inserted into the joint space through a small incision).
- restoring the blood flow to the area by subchondral drilling
- fixing partially detached fragments with pins and screws
- removing any loose fragments in the joint space
- full thickness lesions (where the fragment has completely detached from the bone) can be treated with implanting cartilage-forming cells at the site (autologus chondrocyte implantation) or by replacing the damaged tissue with healthy tissue taken from the same patient (OATS = Osteochondral Autograft Transfer).
Arthroscopy involves less post-operative discomfort and a speedy recovery with little risk of complications. However, it may not be applicable in every case.
Recovery takes a few months after the operation. There is a period of immobilisation or passive mobilisation, followed by physiotherapy and a gradual return to normal activity level.