Knee Irrigation Eases Pain Via ‘Placebo Effect’

By Charnicia E. Huggins

NEW YORK, Jan 30 (Reuters Health) – Irrigating the knee to remove calcium deposits and other debris has long been thought to reduce the pain of osteoarthritis. Now, new study findings suggest that the benefits of this treatment may largely be due to a placebo effect, in which patients feel better simply because they expect the treatment to work.

In tidal irrigation, saline fluid is pushed into and withdrawn from the joint capsule within the knee through a needle to reduce pain resulting from inflammation caused by accumulated debris. The joint capsule is a saclike structure enclosing the joint that contains a lubricating fluid.

“Joint injection therapies, including tidal irrigation, may provide symptomatic benefit for variable lengths of time, (but) at least some of the benefit is attributable to a placebo effect,” Dr. John D. Bradley of the Indiana University School of Medicine in Indianapolis, told Reuters Health.

Bradley and his colleagues studied 180 individuals with knee osteoarthritis who were randomly assigned to a study group that received tidal irrigation or a comparison group that received a sham irrigation treatment, in which the needle did not puncture the joint capsule.

At follow-up, the investigators found that the study groups’ improvement in knee swelling and tenderness, pain, stiffness and walking speed was nearly identical to that seen in the comparison group, according to the report in the January issue of Arthritis & Rheumatism. In fact, the comparison group exhibited a slightly greater, albeit insignificant, improvement.

Neither group, however, showed a significant improvement in the quality of their well-being–such as mobility, physical and social functioning–or their anti-inflammatory or painkiller use.

These study results “demonstrate that placebo effects can be ‘durable,'” Bradley said, noting the 12-month follow-up period incorporated into the study.

In light of the findings, “we have to be very careful about assuming, based on observational studies, that medical treatments–and particularly invasive medical procedures–are effective,” he said.

“The key elements of medical osteoarthritis management remain exercise, weight reduction, minimization of injury and pain control medications,” Bradley concluded.

SOURCE: Arthritis & Rheumatism 2002;46:100-108

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