This recent study from the British Medical Journal shows the common procedure of multiple injections of hyaluronan into the knee joint from osteoarthritis is no better than placebo and is not effective.
We unfortunately commonly see medical procedures used extensively for long periods of time before being subjected to more rigorous studies and being shown to be ineffective or much less effective than previously thought.

Intra-articular hyaluronan is without clinical effect in knee osteoarthritis: a multicentre, randomised, placebo-controlled, double-blind study of 337 patients followed for 1 year

Santolin Chiropractic Clinic