PRP no better than placebo for knee OA, despite the hype

Australian research has challenged the increasingly popular practice of intra-articular injections of platelet-rich plasma (PRP) for knee osteoarthritis.

The randomised controlled trial of 3x weekly injections of PRP versus saline placebo has found no significant difference in knee osteoarthritis symptoms or joint structure at 12 months.

The study comprised 288 adults >50 years of age with knee pain on most days, a knee pain score of ≥4 on an 11-point numerical rating scale, and radiographic evidence of mild to moderate OA.

The study, published in JAMA, found there was no statistically significant, between-group difference in the change in pain scores from baseline to 12 months (−0.4 [95% CI, −0.9 to 0.2] points).

“For percentage change in medial tibial cartilage volume, the between-group mean difference was not statistically significant (−0.2% [95% CI, −1.9% to 1.5%]), with a mean change of −1.4% (SD, 7.2%) in the PRP group and a mean change of −1.2% (SD, 7.2%) in the placebo group.”

“These findings do not support use of PRP for the management of knee OA,” the study said.

In secondary outcomes, there was no statistically significant beneficial effect of PRP on overall pain at the 2-month time point.

“None of the other 24 secondary outcomes that measured symptoms at 2 and 12 months were statistically significantly different between the 2 groups, except for global improvement.”

“More participants in the PRP group than in the placebo group reported global improvement in function at 12-month follow-up (PRP group, 59/138 [42.8%] vs placebo group, 45/140 [32.1%]; risk ratio, 1.36 [95% CI, 1.00-1.86]; P = .05).”

The study said adverse events were minor and transient with more participants in the PRP group reporting knee joint pain, swelling, and stiffness after injections.

The investigators, led by Professor Kim Bennell from the University of Melbourne, concluded that a short course of intra-articular PRP injections did not improve pain or slow disease progression.

“Thus, the trial results do not support use of this procedure (with a mean cost per injection reported as $2032) for treating knee OA.”

An accompanying editorial said the Australian trial was more rigorous than previous trials, “especially with respect to blinding of patients and assessors”.

And the findings were consistent with the American College of Rheumatology and the Osteoarthritis Research Society International (OARSI) recommendations against use of PRP for OA.

Dr Jeffrey Katz, Director of the Orthopaedic and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital and a past president of OARSI, said it was possible however, that a 1-year follow-up period may be too short to observe a beneficial effect.

He said while platelet-rich plasma was “a particularly appealing therapy”, it had not yet lived up to its promise.

Similarly, other recent trials do not support the use of PRP in ankle OA or Achilles tendinopathy.

“Until a new generation of trials using standardised approaches to PRP therapy provides evidence of efficacy, it would be prudent to pause the use of PRP for OA and Achilles tendinitis,” he concluded.

Back to basics

Professor Bennell told the limbic that it was disappointing to have another null study – even when in line with current guidelines.

“Some studies had shown there was some benefit and certainly laboratory research in animals and cells had shown some benefit so there was some evidence that maybe it does work and anecdotally people thought it worked so we were hopeful.”

“On the other hand, we know there is a large placebo effect in knee OA. Our results don’t support recommending it over placebo,” she said.

Professor Bennell said unfortunately people were attracted to quick fixes.

“There are core recommended treatments that are out there which people aren’t doing – exercise and weight loss. People with knee OA should be doing those rather than looking for other treatments.”

She said her team had produced and tested a free, self-directed exercise program which was shown to be beneficial at improving knee pain and function at 24 weeks.

The program My Knee Exercise is freely available online and has had over 10,000 people sign in to date.

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