381 patients with knee osteoarthritis (OA) were randomized to receive intra-articular injections with either Synovail (highly purified intra-articular hyaluronic acid) or Synvisc (hylan G-F20) once a week for three weeks. This double blinded randomized trial examined the efficacy and non-inferiority of Synovial treatment in patients with OA of the knee. The results from this study indicate that both treatments provide significant reductions in the WOMAC Index pain sub-scores at 6 months. Comparisons of mean WOMAC Index pain sub-score decreases from baseline between groups indicate that the treatments are equivalent.