Platelet-Rich Plasma for Knee Osteoarthritis: A Comprehensive Narrative Review of the Mechanisms, Preparation Protocols, and Clinical Evidence.

BACKGROUND

Platelet-rich plasma (PRP) is increasingly utilized for managing knee osteoarthritis (KOA), yet its clinical value remains debated due to the variability in preparation protocols and outcome measures.

METHODS

This narrative review synthesizes current evidence from 40 high-quality studies published between 2013 and March 2025, including randomized controlled trials, systematic reviews, and meta-analyses. The biological mechanisms, clinical effectiveness, safety, and implementation challenges of PRP therapy in KOA are examined.

RESULTS

PRP injections-particularly leukocyte-poor PRP-demonstrate superior pain relief and functional improvement compared to hyaluronic acid and corticosteroids, especially in patients with mild to moderate KOA (Kellgren-Lawrence grades I-III). However, heterogeneity in PRP formulations (platelet/leukocyte content and activation protocols), injection regimens, and follow-up durations limits direct comparability across studies. Evidence from high-quality placebo-controlled trials shows inconsistent long-term benefits, with some failing to demonstrate superiority over saline beyond 6-12 months. The GRADE assessment rates the overall certainty of evidence as moderate. PRP appears safe, with few adverse events reported, but remains costly and variably reimbursed. Guidelines from major societies remain cautious or inconclusive.

CONCLUSIONS

PRP is a promising, safe, and well-tolerated option for early to moderate KOA. However, the standardization of preparation protocols, patient selection criteria, and outcome reporting is essential to improve comparability and guide clinical practice.