Osteochondritis Dissecans

Osteochondritis dissecans (OCD) is a condition in which a small patch of bone just under the cartilage of the knee softens and weakens. It mostly affects active children, teenagers and young adults. If you are reading this for your child, the same advice applies, and Dr Vishal Pai will explain each step to you both. This page explains what causes it, the symptoms, how it is diagnosed and treated, and when surgery is considered.

What is osteochondritis dissecans?

The ends of the bones in your knee are covered with smooth articular cartilage. Under the cartilage is a thin layer of supporting bone (subchondral bone). In osteochondritis dissecans, a patch of this bone loses some of its blood supply and becomes soft. The cartilage over it is often normal at first. If the patch does not heal, the bone and cartilage can crack and start to separate, and a piece can come loose and float inside the knee (a loose body). In a study of about 200 children and teenagers, nearly two-thirds of lesions were on the inner rounded end of the thigh bone (the medial femoral condyle).^[1] Others are on the outer side, in the groove for the kneecap or on the back of the kneecap.

Stable and unstable lesions

A lesion is called stable when the piece is still firmly attached and the cartilage over it is intact. It is unstable when the piece has cracked, partly separated or come loose. Whether a lesion is stable is the main thing that decides treatment.

Juvenile and adult osteochondritis dissecans

Juvenile OCD is found while the growth plates (the bands of growing cartilage near the ends of the bones) are still open. Adult OCD is found after they have closed. It can start in adulthood or be a childhood lesion that never healed. Juvenile lesions are much more likely to heal without surgery.^[3]

What causes osteochondritis dissecans?

The exact cause is not known. Most likely it is a mix of repeated small stresses on the bone from sport, a poor blood supply to that area, and the genes you inherit. Things that make it more likely include:

• Age. Teenagers aged 12 to 19 have about three times the risk of children aged 6 to 11.^[1]
• Being male. Boys have almost four times the risk of girls.^[1]
• Regular sport with running, jumping or pivoting.
• Family history. In one study, about 1 in 7 children treated for OCD had a relative who had also had it.^[4]

What are the symptoms of osteochondritis dissecans?

Symptoms are often mild at first, so OCD can go unnoticed for months. Common symptoms include:

• An ache in the knee that is hard to pinpoint and is worse during or after sport.
• Mild swelling after activity.
• A limp, or walking with the foot turned out to ease the pain.
• Catching, clicking or locking of the knee, or the knee giving way. These are more likely when the piece is unstable or loose.

Some people have no symptoms, and the lesion is found on an X-ray or MRI taken for another reason. OCD can affect both knees. In a large study of children and teenagers, 7 in 100 had lesions in both knees.^[1]

When should you see a doctor?

See your GP or physiotherapist if knee pain with sport lasts more than a few weeks, for you or your child. Seek medical advice sooner if:

• The knee locks, catches or gives way.
• The knee swells.
• You cannot put weight on the leg, or there is a new limp.
• The pain stops normal walking or sleep.

How is osteochondritis dissecans diagnosed?

The doctor will ask about the symptoms and examine the knee. X-rays of both knees, including a view taken with the knee bent (a tunnel view), often show the lesion and whether the growth plates are open. An MRI scan shows the size of the lesion and whether the cartilage over it is intact. Repeat X-rays or MRI scans every few months show whether the lesion is healing.

How is osteochondritis dissecans treated without surgery?

For a stable lesion in a child or teenager whose growth plates are open, non-surgical care is the usual first treatment. In a study of 47 stable lesions, about two-thirds were healing after six months of activity changes and bracing.^[2] Results vary between studies. A review of 27 studies and 908 knees found an overall healing rate of about 61%, with a wide range.^[3] Adults with a stable lesion can also try non-surgical care, but healing is less likely once the growth plates have closed.^[3]

A break from sport

The main treatment is to stop running, jumping and pivoting sports while the bone heals, usually for several months. Of the non-surgical options studied, a break from sport and strenuous activity had the most support.^[3] Low-impact activity may be allowed if it does not cause pain. For a young athlete this is a long break, and the aim is to protect the joint surface for the decades ahead.

Crutches and braces

Crutches or a brace are sometimes used for a few weeks if walking is painful. The review found no clear evidence that keeping the knee still or limiting weight-bearing improves healing.^[3] In a study of 333 knees, an off-loading brace was no better than other non-surgical care.^[5]

Physiotherapy

A physiotherapist can keep the knee moving, strengthen the thigh and hip muscles, and guide a gradual return to sport once the lesion has healed.^[3]

Regular review and repeat X-rays

Dr Vishal Pai reviews you every 3 months with an X-ray and an examination of the knee, checking for swelling or tenderness. A return to full sport is planned once the X-rays show healing and the knee is pain-free.

When is surgery considered?

Surgery is considered when a lesion is unstable or loose, when a stable lesion has not healed after several months of non-surgical care, and in many adults. In a large group of children and teenagers, about 1 in 3 knee lesions went on to surgery, and teenagers were more likely to need it than younger children.^[6] Depending on the lesion, the options include drilling to help a stable lesion heal, fixing a loose piece back in place, or a cartilage repair procedure if the piece cannot be saved. Where possible, surgeons try to keep the original piece, because removing it is linked with more arthritis later.^[7] You can read about these operations on the cartilage repair page.

What is the outlook for osteochondritis dissecans?

Most children and teenagers with juvenile OCD do well. A lesion is less likely to heal without surgery if it is large, if you are older or your growth plates have closed, if the knee was swollen or locking at the start, or if you also have a discoid meniscus.^[3] Keeping to a healthy weight and coming back for review if symptoms return both help protect the knee.

References