Objective To study the long-term outcome of arthroscopy in patients with chronic patellofemoral pain syndrome (PFPS), the authors conducted a randomised controlled trial. The authors also investigated factors predicting the outcome in patients with PFPS.

Methods Fifty-six patients with PFPS were randomised into two groups: an arthroscopy group (N=28), treated with knee arthroscopy and an 8-week home exercise programme, and a control group (N=28), treated with a similar 8-week home exercise programme only. The primary outcome was the Kujala score on pain and function at 5-year. Secondary outcomes were visual analogue scales (VASs) to assess activity-related symptoms.

Results According to the Kujala score, both groups showed a marked improvement during the 5-year follow-up: a mean improvement of 14.7 (95% CI 9.9 to 19.4) in the arthroscopy group and 13.5 (95% CI 8.1 to 18.8) in the controls. No differences between the groups in mean improvement in the Kujala score (group difference 1.2 (95% CI –8.4 to 6.1)) or in the VAS scores were found. None of the investigated factors predicted the long-term outcome, but in most of the cases the treatment result immediately after the exercise programme remained similar also after the 5-year follow-up.

Conclusion Our RCT, being the first of its kind, indicates that the 5-year outcome in most of the patients with chronic PFPS treated with knee arthroscopy and home exercise programme or with the home exercise programme only is equally good in both groups. Some of the patients in both groups do have long-term symptoms.

Trial registration Current Controlled Trials ISRCTN 41800323.