Osteochondritis Dissecans of the Knee
Updated: Jul 24, 2019
Understanding Osteochondritis Dissecans
Osteochondritis Dissecans (OCD) can be a difficult diagnosis to make and an even more difficult diagnosis to understand. In the current literature, there still is no complete understanding of this condition or the underlying cause. OCD is thought to affect the bone that lies just beneath the cartilage, which is also referred to as subchondral bone. For unclear reasons, the subchondral bone undergoes stress and there is a resulting destruction of this bone. If allowed to progress, the cartilage overlying the damaged bone can be damaged or even break off. One leading theory is that the repetitive trauma associated with sports participation can cause microfractures and decreased blood flow to these areas resulting in the development of OCD. However, this cannot explain the entire condition as I have seen this develop in relatively inactive kids as well.
OCD can occur in various joints in the body, but the knee is one of the most common areas that I will see this condition. As chronic knee pain is extremely common, OCD is not the first diagnosis to be considered, which can delay the diagnosis. The presentation is very similar to runner’s knee (patellofemoral syndrome), where an athlete may simply have vague knee pain with running, squatting or lunging and typically not associated with trauma. If the lesion has progressed to a more unstable stage, patients may report painful catching, locking or clicking with movements of the knee.
Ins and Outs of Imaging
The first step in the diagnosis is to obtain a set of x-rays looking at several aspects of the knee. In general, I obtain four specific views of the knee to look specifically for an OCD among other diagnoses. The four view knee series that I prefer includes an AP (front-to-back), Lateral, Sunrise and Tunnel Views. OCD can occur in different areas of the knee, but the most common area is on the lateral aspect of medial femoral condyle (see below). Keep in mind, that a simple AP view x-ray may miss osteochondritis dissecans of the femoral condyle, therefore a tunnel view is critical to visualize the entire knee.
Once the diagnosis is suspected on x-ray, it should be confirmed and further characterized with an MRI. The MRI can tell us further detail about the health of the overlying cartilage as well as the underlying bone. A grading system exists to further determine the nature of the injury. Grade 2 injuries and below are usually treated non-operatively, where as, Grade 3 injuries and above usually require surgery due to the displacement of the overlying cartilage. Below is an example of an OCD with intact overlying cartilage.
Typical non-operative treatment involves 3-6 months of limited pounding activities. The first step involves restricting activity and possibly immobilization in order to control pain. In my experience, if successful, this usually occurs within 6 weeks of rest from physical activity. I often will start the patient back to some physical therapy for the next 6 weeks, which would complete 3 months of rest. Usually, we will re-evaluate the x-ray in 6-8 weeks intervals to see if improvement has occurred. If the patient has had a resolution of pain after 3 months, we can gradually clear the athlete back to sports. Some providers will continue to monitor the lesion yearly until complete healing. If pain has not completely resolved, younger patients may opt to wait another 2-3 months to see if it will heal. It is generally thought that as the growth plates close the potential for healing is decreased. Although the timeline is controversial, if radiographic healing is not seen or clinical healing is not appreciated surgical intervention may be recommended. There are multiple ways to treat osteochondritis dissecans depending upon the age of the patient and the grade of the lesion, which makes a standardized approach difficult to implement.