Osteochondritis dissecans (OCD) is the general heading given to a series of degenerative joint diseases, all of which center on the inflammation or detachment of cartilage from the joint surface.
All joints in the human body have a number of common characteristics. A joint is created by the meeting of two or more bones. The joint is stabilized and supported by ligaments, which connect the bones of the joint together; the nature and extent of the movement of the joint is determined by the configuration of the bones in the joint; a hinge joint such as the elbow will move differently than the hip, which has a ball and socket construction.
At the epiphysis, or end, of the bones that form joints, there is usually a condoyle, a rounded segment on the bone surface that makes the movement of the bone against the opposite side of the joint easier. The condoyle portion of the epiphysis is covered by articular cartilage, a layer of slick, frictionless material that both provides ease of movement for the joint as the bones move against one another, as well as a degree of additional cushion to absorb the forces directed against the end of the bones.
OCD arises when a fragmentary piece of cartilage, most often with a piece of bone attached, separates from the surface of the condoyle. The fragment may remain on the surface of the articular surface, where it appears, if observed by way of x ray, as a lesion. Most often, the fragment will float loosely within the joint space, which is filled with synovial fluid. When the fragment moves into the space between the bones of the joint, the fragment will often prevent the full extension and consequent range of motion of the joint. The result is both a loss of full movement and significant discomfort. The person will often experience significant pain during an athletic activity, and a corresponding stiffness in movement at other times. In some circumstances, due to the position and the size of the loose fragment, the joint, particularly a knee or elbow joint, will seem to "stick" as the athlete attempts to fully extend the structure, much like a sensation experienced when the transmission on a motor vehicle that does not function properly when moving from gear to gear.
OCD is caused most often by a trauma or series of traumas absorbed by the affected joint. A related cause is ischemia, the restriction or loss of blood supply to a part of the body. When the bone to which the cartilage is attached has its blood supply interrupted, the fragmentation of the cartilage may occur. The most common site for the onset of OCD is the knee; the condoyle located on each side of the bottom of the femur (thigh bone) are the areas where cartilage and bone fragments most frequently become dislodged. The elbow is the second most likely structure to sustain an OCD occurrence; OCD in the elbow is sometimes referred to as bone chips. A less common location for OCD is the ankle joint, at the talar dome, the rounded portion of the talus (ankle bone).
Athletes account for approximately 60% of all diagnosed cases of OCD. OCD often occurs in athletes whose bones have not yet reached full maturity, as the articular cartilage and underlying bone in the epiphysis is not developed. Athletes engaging in contact sports, gymnasts, and baseball players form the largest group of persons injured through OCD. Research confirms that over 40% of the athletic injuries involved one or more significant traumas to the knee.
The diagnosis of the injury and the determination of the most appropriate treatment options depends on the elimination of all other possible causes. In the knee, the OCD symptoms are similar to those of a fracture and a serious sprain. A partial tear of the meniscus (the cartilage-like cushioning device on each side of the interior of the knee joint) can also result in loose cartilage pieces being present in the joint. Both x-ray images and magnetic resonance imaging (MRI) technology can isolate the precise location of the fragment. In many cases, arthroscopic surgery can remove the offending object. In some circumstances of elbow OCD, young athletes, often injured through baseball pitching, have successfully had the damaged portion of the articular cartilage grafted onto the bone surface. When the fragment is surgically removed, the typical recovery time from procedure to full resumption of sports is a minimum of three months.
OCD is of particular long-term concern to athletes. OCD carries the additional risk of the development of osteoarthritis, the chronic inflammation and deterioration of the cartilage in the affected joint, at a rate of incidence that is far higher than that of the general population.