PRP Injections for the Treatment of Knee Osteoarthritis: Clinically Significant and Influenced by Platelet Concentration
Bensa A · The American Journal of Sports Medicine (2025)
DOI: 10.1177/03635465241246524This 2025 meta-analysis pooled 18 RCTs with 1995 patients comparing PRP to placebo injections for knee OA. It is the most recent and methodologically rigorous analysis of PRP versus placebo (rather than HA). The key finding was that platelet concentration is the decisive variable: high-concentration PRP (greater than or equal to 1 million platelets per microliter) produced clinically significant and sustained benefit, while low-concentration preparations failed to outperform placebo at 12 months.
Clinical Relevance
The most clinically actionable meta-analysis for PRP in knee OA. Provides the evidence base for a minimum platelet concentration threshold. Clinicians should verify their preparation system achieves >=1 million platelets/uL to expect meaningful patient outcomes.
Key Takeaways
- 18 RCTs, 1995 patients (largest PRP vs placebo analysis for knee OA)
- High platelet concentration (>=1M/uL) produced significant benefit
- Low platelet concentration failed at 12 months
- Establishes a clear concentration threshold for clinical efficacy
- Reconciles conflicting trial results by identifying the key moderating variable
Key Findings
PRP was statistically and clinically superior to placebo at all follow-up points. High-platelet PRP maintained clinically significant improvement at 12 months; low-platelet PRP did not.
Clinical Context
Study Design
Systematic Review and Meta-Analysis
Condition
Knee Osteoarthritis (meta-analysis)
Sample Size
1995 patients
Follow-up
12 months
Control Group
Saline Placebo (18 RCTs)
Primary Outcome
VAS and WOMAC vs MCID
PRP Protocol & Intervention
Preparation System
Various (18 RCTs)
Leukocyte Status
Various
Platelet Concentration
High-platelet (≥1M/µL) vs Low-platelet (<1M/µL)