Study: Diclofenac Better for Knee Osteoarthritis

Diclofenac is more effective than acetaminophen in treating osteoarthritis (OA) of the knee, according to a study reported in the Jan. 27th issue of the Archives of Internal Medicine.

Only one small study has shown acetaminophen to have a statistically significant effect relative to a placebo for the treatment of knee OA. Nevertheless, acetaminophen is recommended as first-line therapy for this condition.

Putting current beliefs about acetaminophen to the test, researchers compared it, the nonsteroidal anti-inflammatory drug (NSAID) diclofenac sodium and a placebo in 82 subjects with symptomatic medial knee OA.

At 2 and 12 weeks, clinically and statistically significant improvements were seen in the diclofenac-treated group, but no significant improvements were seen in the acetaminophen-treated group.

"Our main conclusion is that doctors and and organizations such as the American College of Rheumatology should re-consider recommending acetaminophen," study author Dr. John P. Case, of Rush Medical College in Chicago told Medical Week.

Case said the study suggests with caveats that people who suffer with OA of the knee should be taking diclofenac or other almost any other NSAID instead of acetaminophen.

"If they happen to be taking acetaminophen and having no pain, there
is no reason to switch," Case said. "If they have taken acetaminophen in the past without efficacy, then they should avoid it, since the study suggests it does not work."

For sufferers of knee OA who have never taken acetaminophen for their arthritis pain, Case said it is conceivable that the drug might help them.

"So it is perhaps worth it to try acetaminophen, especially since obtaining prescription-strength NSAIDs means a visit to the doctor," he said. "But the study suggests it won't be likely to help. Still, it is cheap and rather safe."

Other sources: Archives of Internal Medicine 2003;163:169-178