By Dr. Eric W. Edmonds
In the world of childhood knee injuries and complaints, there are few mysteries that still persist.
Most areas of scientific inquiry concerning the knee revolve around the major ligaments and our knowledge of these injuries is so far advanced that often the remaining questions are minor fine-tuning. However, even though it was first described in 1888 by German surgeon Franz König, osteochondritis dissecans (OCD) of the knee remains an enigma.
The leading thought as to why knee OCD happens relates to the thin layer of growth cartilage that caps the end of long bones, such as the femur or thigh bone. When, for example, repetitive trauma results in a blood supply injury or blunt injury to this growth cartilage, then the bone can either fail to develop from the original cartilage, or the maturing bone dies, softens and collapses. It is a process that evolves over a few years.
The risk with an OCD is that the compromised segment of bone and cartilage may come loose, break away from the femur and float around inside the joint.
Although many surgeons feel that surgery is the more conservative treatment with less risk and improved outcomes, it is not universally accepted as the initial treatment. The savviest of surgeons will take into consideration the age of the child, activity level and the radiographic findings.
Once your treating physician confirms that an OCD is present on X-ray, and that there is no evidence to suggest a second diagnosis as the source of pain, treatment should begin with further diagnostic evaluation and rest.
The next test is a magnetic resonance imaging (MRI). The MRI will tell us the true size of the lesion, location of the lesion, and demonstrate evidence of potential looseness. The summation of these MRI findings may be predictive of OCD progression or ability to heal without surgery.
The MRI findings and child age play a large factor in prognosis. The younger the patient and the smaller more stable appearing the OCD, the better the outcome and prognosis to heal.
Children with the better prognosis can be treated conservatively at first. This requires a period of activity modification and even bracing or casting during this rest period. If there is no improvement in the X-rays or the symptoms, then surgery may be beneficial. Moreover, if the OCD is large or unstable, then surgery is a good first choice of treatment.
Surgery may include removing or fixing loose pieces, or stimulating the OCD to heal by drilling it with a small wire. Even with surgery, OCD often requires a long period of rest from sports to allow for healing.
Eric W. Edmonds, M.D., is a pediatric and adolescent orthopedic sports medicine specialist at Rady Children’s Hospital-San Diego and an assistant professor at UC San Diego.