Platelet-Rich Plasma (PRP) is plasma with many more platelets than what is normally found in blood where the concentration of growth factors can be 5 to 10 times higher (or richer) than standard. Many clinical studies have revealed that PRP injections have ameliorated function and diminished pain to various ailments, like elbow, wrist, shoulder, hip, knee, and ankle tendonosis. The researchers here have used meta-analysis mthods to estimate the efficacy and safety of platelet-rich plasma (PRP) injections for the treatment knee of osteoarthritis (OA).

A systematic literature search was implemented in PubMed, Embase, Scopus, and the Cochrane database through April 2016. This was done to reveal Level I randomized controlled trials that assessed the clinical efficacy of PRP versus control treatments for knee OA. The primary outcomes depicted Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function scores. The primary outcomes were differentiated with their minimum clinically important differences (MCID)—defined as the smallest difference recognised as significant by the average patient.

A total of 1069 patients in 10 randomized controlled trials were considered. As per the analysis at 6 months postinjection, PRP and hyaluronic acid (HA) had similar effects with respect to pain relief (WOMAC pain score) and functional advancement (WOMAC function score, WOMAC total score, International Knee Documentation Committee score, Lequesne score). PRP was concerned with notably better pain relief (WOMAC pain score, mean difference −2.83, 95% confidence interval [CI] −4.26 to −1.39, P = .0001) and functional improvement (WOMAC function score, mean difference −12.53, 95% CI −14.58 to −10.47, P  < .00001; WOMAC total score, International Knee Documentation Committee score, Lequesne score, standardized mean difference 1.05, 95% CI 0.21-1.89, P = .01) than HA at 12 months postinjection. Also, the effect sizes of WOMAC pain and function scores at 12 months transcended the MCID (−0.79 for WOMAC pain and −2.85 for WOMAC function score). The PRP was more effective for pain relief (WOMAC pain score) and functional improvement (WOMAC function score) at 6 months and 12 months postinjection, and the effect sizes of WOMAC pain and function scores at 6 months and 12 months surpassed the MCID as compared with saline. PRP did not escalate the risk of adverse events compared with HA and saline.

The evidences obtained from this study specify that, intra-articular PRP injection may have more advantage in pain relief and functional improvement in patients with symptomatic knee OA as compared with HA and saline at 1 year postinjection.