Intra-articular hylan G-F 20 (Synvisc®) in the management of patellofemoral osteoarthritis of the knee (POAK)

The clinical effect of intra-articular viscosupplementation has been assessed in patients suffering tibiofemoral osteoarthritis and review of the data suggest pain relief extending to 12 months in such patients. There are no prospective trials of viscosupplementation targeting patients with patellofemoral osteoarthritis (POAK) of the knee, which is frequent, associated with anterior knee pain and often disabling. This pilot study addressed the therapeutic and adverse effects of intra-articular (IA) hylan in patients with evidence of lone POAK. Forty-three outpatients were recruited to receive a (three-injection) course of IA hylan G-F 20 (Synvisc). Patient and clinician global rating and pain on stair climbing improved significantly from 4 weeks post initial injection to 26 weeks. Secondary outcome measures (including the Oxford Knee Outcome Score) were also recorded. Adverse knee events occurred in 18.6% of patients within 48 h, but only two failed to complete the course of injections because of adverse knee events. One hundred and four patients would be required for a randomised controlled trial of IA hylan to effectively demonstrate an effect size of 0.5 (a 15-mm difference between placebo and treatment arm over a 100-mm visual analogue pain scale) with 95% confidence and 90% power, to detect a 15-mm change in VAS (effect size 0.5) with 95% confidence and 90% power. This would require a RCT of 104 patients to detect a 15-mm change in VAS (effect size 0.5) with 95% confidence and 90% power.