This study was a randomized, double-blind, sham procedure-controlled evaluation of tidal lavage as a treatment for knee osteoarthritis. We achieved blinding by raising a drape during the study procedure and mimicking the sensory aspects of tidal lavage, but not flushing the knee, in the sham lavage group. We gave all study participants subcutaneous anesthesia with lidocaine and then bupivacaine and then attempted aspiration of the knee, removing up to 5 ml of synovial fluid for examination and then injecting the knee with 20 ml of bupivicaine.