medwireNews: Intra-articular injections of platelet-rich plasma (PRP) do not reduce knee pain or disease progression for people with symptomatic mild-to-moderate radiographic medial knee osteoarthritis (OA), suggest findings from a randomized controlled trial.
“Although PRP is increasingly used to treat knee OA, evidence to support clinical benefits of PRP is limited,” with current guidelines emphasizing the need for rigorous studies, say the study authors in JAMA.
In the RESTORE trial, the overall knee pain score, measured on an 11-point numeric rating scale for average pain over the past week, improved from a mean of 5.7 points at baseline to 3.5 points at 1 year for the 144 participants who were randomly assigned to receive three intra-articular injections of leukocyte-poor PRP given at weekly intervals.
By comparison, this score decreased from an average of 5.7 to 3.9 points among the 144 participants given placebo injections. The mean improvement met the threshold for a minimum clinically important difference in both groups, and the between-group difference of 0.4 points was not statistically significant.
Similarly, there was no significant difference in the average annual decrease in medial tibial cartilage volume between the PRP and placebo groups, at 1.4% and 1.2%, respectively.
“These findings do not support use of PRP for the management of knee OA,” say Kim Bennell (The University of Melbourne, Victoria, Australia) and co-investigators.
Writing in an accompanying editorial, Jeffrey Katz (Brigham and Women’s Hospital, Boston, Massachusetts, USA) says that the substantial improvements seen in the placebo group of this trial, as well as in the previously reported PRIMA trial of patients with ankle OA, “emphasize the importance of comparing interventions with placebos in trials of injection therapies.”
Katz notes, however, that there was “suggestion of possible benefit for some of the secondary outcomes” with PRP in the RESTORE trial. For instance, a significantly higher proportion of patients given PRP versus placebo reported an improvement in overall status on a 7-point Likert scale (48.2 vs 36.2%).
Taken together with “the mixed results of prior studies” investigating PRP for OA and Achilles tendinitis, these findings “support caution before dismissing PRP entirely for knee OA,” he says.
Katz explains that comparing results across PRP studies is challenging because “protocols for preparing and administering PRP differ among studies, and the “concentrations of platelets and specific growth factors in PRP preparations also vary widely.”
He concludes: “Until a new generation of trials using standardized approaches to PRP therapy provides evidence of efficacy, it would be prudent to pause the use of PRP for OA and Achilles tendinitis.”
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