Tidal irrigation as treatment for knee osteoarthritis - A sham-controlled, randomized, double-blinded evaluation

Objective. To evaluate the effectiveness of tidal irrigation (TI) in comparison with a well-matched sham irrigation (SI) procedure as a treatment for knee osteoarthritis (OA). Methods. One hundred eighty, subjects with knee OA were randomized to receive TI or SI, with clinical followup over the ensuing 12 months. The primary outcomes of interest were change in pain and function, as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Subjects and the nurse assessor were blinded, and success of blinding was assessed. Results. Although the study groups were otherwise comparable, the baseline WOMAC pain and physical functioning scores were higher (worse) in the SI group. After adjustment for baseline, there were no differences between the effects of SI and TI. Blinding was successful, with similar to90% of SI and TI subjects stating that they had received the TI procedure. Conclusion. Most, if not all, of the effect of TI appears to be attributable to a "placebo response.".