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.