Osteochondritis dissecans occurs when a fragment of bone in a joint separates from the rest of the bone because its blood supply is faulty, and there is not enough blood to maintain it. It often affects the knee or the elbow.

Sometimes, the separated fragment stays in place or repairs on its own. However, in the later stages, the bone can splinter and fall into the joint space, resulting in pain and dysfunction. These fragments are sometimes called "joint mice."

The exact prevalence is unknown, but there may be between 15 and 29 cases in every 100,000 people. It is more common in males, especially those between the ages of 10 and 20 years who are physically active.

However, the incidence is increasing in females.

It usually affects teens and young adults, but it can occur in younger children who are active in sports.

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OCD can cause pain and discomfort in the knee and other joints.

Osteochondritis dissecans (OCD) can occur in different joints, including the hip and ankle, but 75 percent of cases affect the knee.

Signs and symptoms of OCD include:

  • inflammation, swelling, and soreness in the joint
  • catching and locking in the joint during movement
  • reduced range of movement in the joint
  • crepitus, a grating, cracking, or popping sound when moving the joint
  • weakness in the joint
  • limping
  • effusion, or abnormal collection of fluid in the joint area, leading to swelling
  • pain, especially after physical activity
  • stiffness after a period of inactivity

The exact cause is unknown, but they may include:

Ischemia: a restriction of blood supply starves the bone of essential nutrients. The restricted blood supply is usually caused by some problem with blood vessels, or vascular problems. The bone undergoes avascular necrosis, a deterioration caused by lack of blood supply. Ischemia usually occurs in conjunction with a history of trauma.

Genetic factors: OCD sometimes affects more than one family member. This may indicate an inherited genetic susceptibility.

Repeated stress to the bone or joint: this can significantly increase the risk of developing OCD. Individuals who play competitive sports are more likely to regularly stress their joints.

Other factors may be weak ligaments or meniscal lesions in the knee.

A person who experiences the symptoms of OCD in a joint should seek medical advice. An early diagnosis can mean more effective treatment and a lower risk of complications.

The doctor will carry out a physical examination and ask the patient about their medical history, family history and lifestyle, including sporting activities.

There may be some imaging tests, such as an X-ray, CT, MRI scan, or ultrasound. This may show whether there is any necrosis, or tissue death, or loose fragments. A bone scan may also be recommended.

In the early stages, tests will show that the cartilage is thickening. In the later stages, there will be loose fragments.

The early stages are considered stable, and treatment is more likely to be effective at this point.

Conditions, with similar symptoms need to be ruled out. These include inflammatory arthritis, osteoarthritis, bone cysts and septic arthritis.

Conservative measures include changes of activity or rest. This can give the bone time to heal and to prevent future fracture, crater formation, or chondral (cartilage) collapse.

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Rest and the use of crutches may help.

If the patient has been involved in sports, they may need to stop for a while.

The doctor may immobilize the joint with a medical device, such as a splint or a brace. Crutches may be necessary.

A non-steroidal anti-inflammatory medication (NSAID) can help with pain. A physical therapist may offer guidance with stretching and specific exercises.

Children can normally return to sports after 2 to 4 months. In young children, OCD normally heals with rest, as the bones are still growing.

In older children and adults, the effects can be more severe.

Surgery

Surgery aims to:

  • restore normal bloodflow
  • get the joint to work normally again

It may be recommended if conservative measures have not worked, if a lesion has become detached and is moving around inside the joint, or if the lesion is over 1 centimeter in diameter.

Drilling into the lesion can create pathways for new blood vessels to form in. This allows blood to flow, and encourages the bone to heal.

The surgeon makes a small incision. Using some long, thin instruments, they either remove or reattach the loose fragments of bone. If the cartilage is still attached to the bone, pins or screws can be used to secure it.

Osteochondral autograft transfer (OATS) uses healthy cartilage to replace damaged cartilage on the surface of the joint that receives weight-bearing stress. It is like a cartilage transplant, but the recipient and donor is the same person.

After surgery the patient will undergo a rehabilitation program. After an initial period of immobilization, physical therapy can help regain joint strength and stability.

According to the American Academy of Orthopedic Surgeons (AAOS), the patient will probably need:

  • crutches for about 6 weeks after surgery
  • physical therapy for 2 to 4 months, to recover strength and motion

After 4 to 5 months, a gradual return to sports may be possible.

Minimally invasive arthroscopic surgery is less painful, the recovery time is faster, and the risk of complications is lower.

Complications

Without treatment, complications may occur. These include pain, functional impairment, recurrent swelling of the joint, and the formation of loose fragments.

Around 5 percent of middle-aged patients with osteoarthritis experienced OCD at a younger age.