Non-steroidal anti-inflammatory drugs (NSAIDs) and intraarticular corticosteroid and hyaluronate injections are the standards of care for osteoarthritis (OA) of the knee. However, long-term NSAID usage can cause gastrointestinal bleeding in some patients. The advent of selective COX-2 inhibitors has reduced this risk, but there remains significant concern with the systemic toxicities of NSAIDs. Intraarticular injections are less likely to cause systemic toxicity, but they have a limited duration of effect (anywhere from 1-8 weeks for corticosteroid injections, and 12-52 weeks for hyaluronate injections) and may have harmful effects on joint integrity. An alternative therapyirrigation of the OA knee, poses minimal local and systemic risks.
Irrigation of the OA knee purports to remove phlogistic and/or abrasive debris from the joint. The procedure has long been believed to reduce pain, and this belief is supported by a number of studies comparing needle irrigation with various other OA treatments. However, none of these studies were both adequately powered and placebo controlled. To address this issue, Bradley et al (Arthritis Rheum 46:100-108, 2002) developed a sham modification of the needle tide irrigation procedure and performed a randomized, double-blinded, sham-controlled investigation of tidal irrigation in knee OA.
One hundred eighty subjects were randomized to receive either the tidal irrigation procedure or the sham irrigation procedure. Tidal irrigation consisted of intraarticular instillation of 50 ml aliquots of sterile normal saline (after intraarticular bupivacaine) and withdrawal, until a total of 1 liter was passed through the knee. In the sham irrigation, the needle was passed through soft tissue but not into the joint capsule. 50 ml aliquots of saline were withdrawn from the bag and discarded, but small amounts (3-5ml) of saline were instilled into the soft tissues around the knee. The 1-liter bag of saline was visible to all patients during the procedure. Clinical follow-up was performed at 3, 6 and 12 months after the procedure. The primary outcomes were changes in pain and function as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Subjects and the nurse assessor were blinded.
The study groups were comparable in demographic features as well as in their weight, duration of knee arthritis, and radiographic severity of knee OA. However, in the sham irrigation group, baseline WOMAC scores were more severe. After adjusting for baseline WOMAC scores, there were no differences between the effects of the tidal irrigation and the sham irrigation. Following study treatment, the sham and tidal irrigation groups showed essentially identical improvement in WOMAC scores, global assessments, 50-foot walk times and knee swelling and tenderness. Blinding was successful with approximately 90% of the subjects guessing they had received the tidal irrigation procedure.
The effect of tidal irrigation appears to be attributable to a “placebo response”.
This is a long overdue and important study. The methodology employed here utilized a non-surgical approach. However, many OA patients receive recommendations for surgical irrigation of their knees, a similar but more invasive procedure for which rigorous placebo-controlled studies are also lacking.