As the seven-time All-Star Tracy McGrady of the Houston Rockets checks out for season-ending microfracture surgery on his knee, new attention has been focused on cartilage injuries in athletes. Cartilage injuries in the knee are not uncommon in collegiate and professional athletes of all sports, although contact and high-impact activities are particularly high-risk.
There are two types of cartilage in the knee: articular cartilage and the meniscus. Articular cartilage functions to provide a smooth surface for bones to glide against one another and as a shock absorber. Unlike most tissues in the body the articular cartilage that lines the surfaces of our joints has no inherent ability to regenerate. We are born with what we have and protecting it is of paramount importance, as progressive cartilage injury and loss can initiate the cascade of degenerative wear and arthritis. Focal cartilage injuries from trauma can affect any of the surfaces of the knee including the femoral, tibial, and patellar surfaces. Bipolar or “kissing” defects occur when opposing surfaces of a joint are have pathologic lesions, and these are among the most difficult and problematic to treat.
For athletes, cartilage injuries often result from a twisting or pivoting motion. Patients will often complain of sharp pain in the knee, usually localized to the area of the cartilage injury. Swelling, catching, clicking or locking in the knee may occur. Xrays and MRIs are both extremely useful in diagnosing the condition. Certain cartilage injuries respond well to a period of rest, anti-inflammatory medication, and physical therapy. Sometimes, however, surgery is necessary. If a piece of cartilage is missing, leaving exposed bone, the goal of surgery is to try to fill the defect with repair tissue that is as similar to native cartilage tissue as possible.
According to Dr. Thomas Wickiewicz, a sports medicine specialist at The Hospital for Special Surgery and the former president of the American Orthopedic Society for Sports Medicine, “Microfracture surgery has become a widely used first-line treatment for focal cartilage injuries in athletic individuals.” Microfracture is a marrow stimulation that is commonly utilized to treat focal, symptomatic cartilage defects in the knee. In microfracture surgery, small channels are created by the surgeon, which provides access to the bone marrow deep to the cartilage surface. Stem cells can then migrate from the marrow to fill the defect and form an enriched blood clot. The cells then differentiate into a cartilage-like tissue that fills the defect and provides a smooth contact surface. This procedure is done arthroscopically, with patients going home the same day of the surgery.
According to Wickiewicz, “There is variability in the clinical success, but in those that get a reasonable “fill” on the defect with fibrocartilage, the improvements have been noticeable.” Outcomes can be influenced by a number of factors, including the severity and size of the defect, number of defects, patient age, compliance, and rehabilitation. A number of professional basketball players, including All-Stars like Amare Stoudemire, Jason Kidd, and Antonio McDyess, have returned following microfracture surgery and continue to play at the highest level. Others, however, such as Anfernee Hardaway or Jamal Mashburn, returned to the NBA but had difficulty achieving their prior level of play. Wickiewicz concludes that “Lingering concerns about the long term durability of the repair tissue remain,” but hopefully Tracy McGrady will be in the group of players that get back to the NBA to have a long, productive career.