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Despite the increasing trend of PRP in knee osteoarthritis, most clinical guidelines do not recommend it due to a lack of evidence on its efficacy.
New data from Australia suggested that among patients with mild-to-moderate radiographic knee osteoarthritis (OA), intra-articular injection of platelet-rich plasma (PRP) did not result in significant difference in symptoms or joint structure at 12 months of treatment compared with injection of saline placebo.
According to investigators led by Kim L. Bennell, PhD, Department of Physiotherapy, The University of Melbourne, most clinical guidelines have not recommended PRP due to a lack of high-quality evidence on efficacy for symptoms and joint structure.
Despite this, the use of PRP in knee osteoarthritis had been increasing in recent years.
With their current study, Bennell and colleagues evaluated the efficacy of intra-articular PRP injections on symptoms and joint structure in patients with knee osteoarthritis, and hypothesized the treatment would lead to greater improvement in knee pain severity and less medial tibial cartilage volume loss at 12 months compared with placebo saline injections.
Bennell and investigators conducted a 2-group, multi-site, superiority randomized clinical trial dubbed RESTORE.
The trial enrolled community-based volunteer participants from Melbourne and Sydney through broadcast, print, and social media methods, as well as through clinicians and researchers’ volunteer data-bases at the University of Melbourne and the University of Sydney.
All eligible participants were to be 50 years or older, had knee pain during the majority of the preceding month, had an average knee pain score of 4 or higher on an 11-point numerical rating scale in the past week, and had mild-to-moderate radiographic tibiofemoral osteoarthritis.
A total of 288 patients were enrolled in the study, with 269 having completed the trial.
From there, participants were randomized into 2 groups, 1 featuring leukocyte-poor PRP using a commercially available product (144, group 1), and another saline placebo.
Each group received 3 intra-articular knee injections at weekly intervals under ultrasounds guidance using a medial patellofemoral approach.
The 12-month follow-up would be completed on July 22, 2020.
The 2 primary outcomes were 12-month change in overall average knee pain scores (11-point scale; range, 0-10, with higher scores indicating worse pain; minimum clinically important difference of 1.8) and percentage change in medial tibial cartilage volume as assessed by magnetic resonance imaging (MRI).
Additionally, 21 secondary outcomes were established that evaluated pain, function, quality of life, global change, and joint structures at 2-month and/or 12-month follow up.
The investigators reported that treatment with PRP vs placebo injection resulted in a mean change in knee pain scores of −2.1 vs −1.8 points, respectively (difference, −0.4 [95% CI, −0.9 to 0.2] points; P = .17) after the conclusion of the study.
The mean change in medial tibial cartilage volume was −1.4% vs −1.2%, respectively (difference, −0.2% [95% CI, −1.9% to 1.5%]; P = .81). Of 31 prespecified secondary outcomes, 29 showed no significant between-group differences.
There was no statistically significant beneficial effect of PRP on overall pain at the 2-month secondary time point, and none of the other 24 secondary outcomes that measured symptoms at 2 and 12 months were statistically significantly different between the 2 groups, with the exception for global improvement.
Adverse events were minor and transient.
Though limitations were noted, such as the lack of standardization regarding PRP preparations, the investigators were confident that intra-articular injection of PRP did not result in any significant changes in symptoms or joint structure in comparison to injection of saline placebo.
“These findings do not support use of PRP for the management of knee OA,” the team wrote.
The study, “Effect of Intra-articular Platelet-Rich Plasma vs Placebo Injection on Pain and Medial Tibial Cartilage Volume in Patients With Knee Osteoarthritis The RESTORE Randomized Clinical Trial,” was published online in JAMA.