kneeinjectionSince the 1970s, some doctors have treated arthritic knees by injecting them with hyaluronic acid, a substance originally derived from the combs of roosters. Specialists have zealously promoted this therapy, costing patients a few hundred dollars a pop and repeated so widely that Medicare alone pays $300 million annually for it. Doctors argue it reduces pain and increases joint mobility.

It hardly lives up to this billing, though, offering patients scant more relief than a placebo (saline, or salt water), researchers found after scrutinizing a half century’s worth of data from 169 clinical trials involving more than 20,000 patients.

The highly popular viscosupplementation procedure, as reported by Stat, a medical and scientific news site, showed an average effect “about 2 points beyond placebo effect on a pain scale that runs from 1 to 100.” The researchers from Canada, Britain, and China concluded this from their study, as published in BMJ, a respected medical journal of the British Medical Association: