It’s boom time for the global viscosupplementation market, predicted to more than double to $6.5 billion in less than a decade despite ample evidence the treatment does not work.

A recent report by US market research company Grand View Research suggests rising rates of osteoarthritis and obesity are driving worldwide appetite for the hyaluronic acid (HA) injections, which are marketed as a treatment for OA and cost $450-550 each in Australia.

The report predicts the global “reimbursement scenario” will become more favourable towards OA patients using the injections. The US Medicare already reimburses 80% of the patient-allowable cost and some secondary insurers cover the gap, it said.

This is despite numerous trials and meta-analyses showing the efficacy of injectable HA for knee OA is “at best modest and at worst indistinguishable from that of placebo”, according to an  article on the New England Journal of Medicine blog.

Professor Hunter, rheumatology clinician researcher at the University of Sydney, said research into the effects of HA on other joints reached the same conclusions.

The fact HA injections are widely used by musculoskeletal doctors, orthopaedic surgeons, sports physicians and rheumatologists is the result of successful marketing, not evidence-based medicine, he said.

“Most of the recent guidelines don’t encourage these treatments so I don’t know how they keep ignoring the evidence; it’s out there in meta-analyses and individual trials,” Professor Hunter said.

The theory is to inject naturally occurring HA into the joint to replenish supposedly deficient supplies, and lubricate the joint.

“The reality of it is within 24 hours of having an injection of a product like this you can’t find that product within the joint, it all gets washed up into the body. It’s not surprising it does not have any meaningful effect.”

The injections cause swelling of the joint in 5-10% of patients, he said.

“It usually resolves over seven to 10 days but it can be quite painful.”

Some people continue the injections every six to 12 months for years.

“As with any treatment with OA, there is a bigger placebo effect with injectables than if it were a tablet,” Professor Hunter said.

“The therapeutic benefit is not inconsequential, but when we know they can get the same benefit from a saltwater injection without the commensurate risk and the cost, I think it’s hard to justify.”