PRP Injections Show No Significant Improvements in Ankle Osteoarthritis Outcomes


Data show no significant improvement in pain, function and alignment scores over 26 weeks in the PRP injection group, compared to placebo.

In a recent study, a team of investigators, led by Liam D. A. Paget, MD, Amsterdam UMC, University of Amsterdam, looked to determine the effect of platelet-rich plasma (PRP) injections on symptoms and function in patients with ankle osteoarthritis.

They found that in these patient populations, intra-articular PRP injections, in comparison to placebo injection, had no significant improvement in the primary outcomes that assessed pain, function and alignment over a period of 26 weeks.


Entitled the “Platelet Rich Plasma Injections for the Management of Ankle Osteoarthritis (PRIMA)”, the study was a randomized clinical trial aimed to assess efficacy of PRP injections in ankle osteoarthritis. It was performed in 6 centers in the Netherlands.

Eligibility for patients included ages ≥18 years, with a score of ≥40 for ankle osteoarthritis pain severity on a visual analog scale (0 - 100, higher score indicating more severe pain) during daily activities, as well as radiographic imaging indicating at least grade 2 tibiotalar osteoarthritis on the van Djk classification.

Then, randomization assigned participants 1:1 to receive 2 ultrasonography-guided intra-articular injections of PRP or a saline placebo. Patients received the injections 6 weeks apart.

Primary outcomes for the study consisted of the American Orthopedic Foot and Ankle Society (AOFAS) score over 26 weeks. The score ranged from 0 - 100, with higher scores indicating less pain and better function. It measured 3 subdomains including pain (40 points), function (50 points), and alignment (10 points).


Enrollment for the study began in August 2018 and the last 26-week follow-up occurred in December 2020.

A total of 320 patients had been assessed for eligibility, from which 100 were enrolled in the trial and randomized to either PRP (n = 48) or placebo (n = 52). The mean age of participants was 56 years, with 45% women. No patients were lost to follow-up in the primary outcomes.

At baseline, data show the mean AOFAS scores were 63 in the PRP group and 64 in the placebo group. Then, at the 26-week follow-up, mean scores were shown to improve by 10 points in the PRP group (95% CI, 6 - 14, P <.001), in comparison to 11 points in the placebo group (95% CI, 7 - 15, P <.001).

Data show the adjusted between-group differences of PRP versus placebo over 26 weeks was -1 point (95% CI, -6 to 3, P = .56) During the post-hoc sensitivity analysis, no statistically significant between-group differences of PRP versus placebo was observed (-2 points, 95% CI, - 5 to 11, P = .16).

Additionally, the placebo group reported 1 serious adverse event, deemed unrelated to the intervention, with 13 other adverse events in the PRP group and 8 in the placebo.


Investigators noted that ankle symptoms and function did not show significant improvement over 26 weeks with intra-articular injections, compared to placebo, in patients with ankle osteoarthritis.

“The likelihood of clinically relevant benefit is small, because the minimum clinically important difference was outside the 95% CI of the primary outcome,” they wrote.

The study, “Effect of Platelet-Rich Plasma Injections vs Placebo on Ankle Symptoms and Function in Patients With Ankle Osteoarthritis,” was published in JAMA.

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