Visually-guided irrigation in patients with early knee osteoarthritis: a multicenter randomized, controlled trial

Objective: To determine if visually-guided arthroscopic irrigation is an ef fective therapeutic intervention in patients with early knee osteoarthritis . Design: Ninety patients with knee osteoarthritis were randomized in a doubl e-blind fashion to receive either arthroscopic irrigation with 3000 mi of s aline (treatment group) or the minimal amount of irrigation (250 mi) requir ed to perform arthroscopy (placebo group). The primary outcome variable was aggregate WOMAC score. Results: The study did not demonstrate an effect of irrigation on arthritis severity as measured by aggregate WOMAC scores, the primary outcome variab le; the mean change in aggregate WOMAC score at 12 months was 15.5 (95% CI 7.7, 23.4) for the full irrigation group compared to 8.9 (95% CI 4.9, 13.0) for the minimal irrigation group (P=0.10). Full irrigation did have a stat istically significant effect on patients' self-reported pain as measured by the WOMAC pain subscale and by a visual analog scale (VAS) (the secondary outcome variables). Mean change in WOMAC pain scores decreased by 4.2 (95% CI -0.9, 9.4) for the full irrigation group compared with a mean decrease o f 2.3 (95% CI -0.1, 4.7) in the minimal irrigation group (P=0.04). Mean VAS pain scores decreased by 1.47 (95% CI -1.2, 4.1) in the full irrigation gr oup compared to a mean decrease of 0.12 (95% CI 0.0, 0.3) in the minimal ir rigation group (P=0.02). A hypothesis-generating post-hoc analysis of the e ffect of positively birefrigent intraarticular crystals showed that patient s with and without intraarticular crystals had statistically significant im provements in pain assessments and aggregate WOMAC scores at 12 months; pat ients with crystals had statistically greater improvements in pain. Conclusions: Visually-guided arthroscopic irrigation may be a useful therap eutic option for relief of pain in a subset of patients with knee OA, parti cularly in those who have occult intraarticular crystals. (C) 2000 OsteoArt hritis Research Society International.