A chondral defect refers to a focal area of damage to the articular cartilage (the cartilage that lines the end of the bones). An osteochondral defect refers to a focal area of damage that involves both the cartilage and a piece of underlying bone. These can occur from an acute traumatic injury to the knee or an underlying disorder of the bone.
This is distinctly different than arthritis and should be thought of differently as the treatments are significantly different as well. Unfortunately, an isolated cartilage defect, without any underlying bone attached to the fragment, is not commonly repairable. The cartilage is often not viable when it is separated from the bone and therefore must be removed which can be done with an arthroscopic procedure. However, the now exposed bone should be treated, if possible, to attempt to stimulate growth of new cartilage. Some healthy flaps of cartilage can be repaired by special techniques. This would need to be discussed in detail with your surgeon.
One technique for treating isolated cartilage defects is called a "microfracture". This technique is suitable for younger to middle age patients with very focal areas of cartilage loss (typically less than 2 square centimeters) and where the remaining cartilage is healthy. During a microfracture (which is typically done arthroscopically), tiny holes are made in the bone to create tunnels to the underlying bone marrow and natural stem cells. Through these tiny channels, the stem cells flow into this area of bone and coat the area where the cartilage is lost. Over time these cells can develop into a new form of cartilage. This process is delicate and requires optimum conditions to be routinely successful. Therefore certain protocols will need to be followed after surgery to protect this area as well as contour the newly forming cartilage.
Another technique, typically reserved for larger areas of loss and some forms of osteochondral defects, is to perform a transplant procedure. Several types of transplants have been described, including taking small plugs of bone and cartilage from other locations in the knee and filling this defect. Often what is required is the use of a fresh donor graft of bone and cartilage that is specifically matched to the size and dimensions of the defect. This can often take months until a suitable donor is available.
An osteochondral defect that is in the early stages may be suitable for a repair technique to keep the native bone and cartilage. This would be the optimal scenario. This requires a detailed evaluation to be performed to assess the integrity of the remaining cartilage, the underlying bone and to look for evidence of healing capacity.
Numerous factors are considered when evaluating these disorders for the correct treatment and each scenario should be discussed in detail with your surgeon. A comprehensive physical exam is required, as are specialized Xrays and an MRI. Occasionally, a specialized test called a bone scan with be utilized to identify if the underlying bone is healthy and prepared for certain techniques. These will be used to determine the type and extent of the damaged area, and for measurement purposes to determine the possible treatment options.