A study has questioned the benefits of platelet-rich plasma injections, an increasingly popular treatment for ailments ranging from arthritis to muscle sprains to fractures.

For platelet-rich plasma therapy, or PRP, doctors draw a person’s own blood, then separate and concentrate cells that generate growth factors. These are then injected into inflamed or slow-to-heal tissues. In theory, this stimulates healing.

The study, which was published in the Journal of the American Medical Association, put that to the test.

Dutch researchers randomly assigned 54 patients suffering from Achilles tendinopathy, a condition where tendon bundles are weakened and people complain of pain just above their heel bone, to receive either platelet-rich plasma injections or a placebo shot of saline.

Both groups also did standard rehabilitation that consisted of 180 heel drops (an exercise in which the toes are placed on the edge of a step and the heels are lowered toward the step below) daily for 12 weeks.

Results showed no difference between the two groups at six, 12 or 24 weeks after the procedure. Both groups improved about 20 points on a standardized scale that measures pain and function.

Robert-Jan de Vos, MD, in the Department of Orthopedics at Erasmus Medical Center, says researchers don’t know why the injections didn’t work and they’re very disappointed by the results.

“These tendon injuries are very hard to treat,” Dr. De Vos says. “We know that less than 50 percent of the patients with chronic Achilles tendinopathy are free of symptoms after one year. We still cannot prescribe a very promising conservative treatment, which is frustrating for the patients and treating doctors.”

Researchers say, at the very least, these results will prevent people from unnecessarily going through the expensive and very painful treatment, which can cost $1,000 to $2,000 per injection and is typically not covered by insurance.

Scientists say they will continue to research treatment of this injury and more studies will be done on other tendinopathy locations, like tennis elbow.

“It is very hard to state whether we can extrapolate these results to other areas,” Dr. De Vos says. “The Achilles tendon is a load-bearing tendon, which is very hard to treat. Future studies on other tendon locations or other tissues might confirm our results.”

Cynthia Harrell is a physical therapist at the Duke Center for Living at Duke University in Durham, NC. She says even though a lot of people are trying PRP, this study proves it is not a reliable treatment right now. 

She says she favors a less-invasive method for treating Achilles injuries – exercises that lengthen muscles. 

“It’s something that may have some promise for the future, but right now it is still very experimental," Harrell says. "I would strongly recommend anyone with this tendinopathy to use [stretching exercises] in their treatment protocol instead.”