Hyaluronic acid injections for knee osteoarthritis. Systematic review of the literature.

OBJECTIVE To determine whether viscosupplementation with intra-articular hyaluronic acid (HA) injections improves pain and function in patients with osteoarthritis (OA) in their knees. DATA SOURCES We searched MEDLINE, Pre-MEDLINE, and Cochrane databases using the MeSH headings and key words osteoarthritis (knee) and hyaluronic acid. STUDY SELECTION English-language case series and randomized controlled trials (RCTs) were selected. Studies with biologic, histologic, or arthroscopic outcomes were excluded. SYNTHESIS Five case series and 13 RCTs were critically appraised. Data from three case series and three RCTs using injections of high-molecular-weight HA (Synvisc) demonstrated significant improvement in pain, activity levels, and function. The beneficial effect started as early as 12 weeks. Studies using low-molecular-weight HA had conflicting results. CONCLUSION Viscosupplementation with high-molecular-weight HA is an effective treatment for patients with knee OA who have ongoing pain or are unable to tolerate conservative treatment or joint replacement. Viscosupplementation appears to have a slower onset of action than intra-articular steroids, but the effect seems to last longer.