Intra-articular hyaluronic acid: duration of effect and results of repeated treatment cycles.

An open-label, multicenter study was designed to evaluate the effects of intra-articular (IA) hyaluronic acid in patients given a diagnosis of osteoarthritis of the knee. Patients (n = 108) received five weekly IA injections of hyaluronic acid 20 mg (Hyalgan) under sterile conditions, and were observed for up to 12 months after the last injection. Some patients received a second series of injections after 4 to 8 months. For the 59 patients who were observed for 12 months after the first treatment cycle, evaluation of pain according to a visual analog scale showed significant improvements lasting 12 months, with pain during load, pain at rest, and duration of walking ability compared with a baseline evaluation. Patients who required a second treatment cycle showed a further amelioration. Significant improvements were also seen in knee function and in global evaluations by both patient and investigators. Relief of symptoms of osteoarthritis of the knee was seen as early as 4 weeks after treatment in 68% of patients receiving IA hyaluronic acid. In 55% of these patients, relief was maintained until the end of the 12-month follow-up.