New Horizons in the Treatment of Osteoarthritis of the Knee

OSTEOARTHRITIS IS NOT SIMPLY A degenerative disorder. Rather, it is a complex derangement of articular surfaces that involves the loss of normal collagen architecture followed by an attempt by chondrocytes to produce replacement cartilage. The replacement surface is less resistant to wear than the original. Over time, fullthickness cartilage loss may develop on the articular surfaces. Symptoms of osteoarthritis include joint pain, typically worse with use and eased with rest, and joint stiffness after nonuse. The pain can become persistent. In the past, failure of symptomatic treatment, such as nonsteroidal anti-inflammatory drugs and physical therapy, has left joint replacement as the principal option in the care of more severely affected patients. However, in recent years, 3 new intra-articular procedures have shown promise for some patients with articular cartilage defects of the knee. Multiyear follow-up has shown encouraging results for these treatments of diffuse osteoarthritis and focal articular defects of the knee. Focal articular cartilage defects, often found in young adults, have been increasingly recognized as a cause of functional problems. To date, only lesions on the femoral condyles and trochlear groove have been effectively treated. Two techniques to treat these lesions, autogenous cartilage implantation (ACI) and autogenous osteochondral grafting, improved knee function in 2to 5-year follow-ups in carefully selected patients. Patients most likely to benefit are those with normal knee alignment, no evidence of ligamentous instability, and no evidence of arthritis on the corresponding tibial surface. In general, the radiographs of these patients’ knees are normal or near normal, with little evidence of joint space narrowing or osteophyte formation in weight-bearing radiographs. For the more common condition of diffuse osteoarthritis of the knee, the Food and Drug Administration has approved the intra-articular injection of forms of hyaluronic acid in more advanced cases. Technically classified as a device rather than a drug, hyaluronic acid compound injection has been used outside the United States, with functional improvement in up to 77% of patients.