Common Drug for Knee Pain No Better Than Placebo

Acetaminophen, known in many parts of the world as paracetamol, is the active ingredient in Tylenol and many other brands of medicine.

Clinical trials have shown that acetaminophen reduces knee pain, but Dr. Maxime Dougados, of Rene Descartes University, Paris, and colleagues say these trials "have been relatively small, and variable daily doses of paracetamol have been used."

The team conducted their own trial, reported in the Annals of the Rheumatic Diseases. They examined the efficacy of paracetamol for treating osteoarthritis of the knee in 779 patients who had knee pain of at least 30 on a 100-point visual scale during physical activity.

The participants were randomly assigned to treatment with 4 grams per day of paracetamol or an inactive placebo, for six weeks. The main outcome target was a 30 percent decrease in pain intensity of the knee.

The proportion of participants who achieved this level of pain relief was almost the same in the paracetamol and placebo groups, at 52.6 percent and 51.9 percent, respectively.

Twenty-six percent of the patients in the paracetamol group and 30 percent of those in the placebo group withdrew from the study. "Withdrawals due to treatment failure were noted in 14 percent and 18 percent in the paracetamol and placebo groups, respectively," the authors write.

Given these findings, Dougados' team says "the use of paracetamol in symptomatic osteoarthritis of the knee might be further explored."

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