PRP for Knee Osteoarthritis

There is growing evidence supporting the use of Platelet-Rich Plasma (PRP) for knee osteoarthritis (OA), but it remains somewhat mixed, with variability depending on the formulation of PRP, the severity of OA, and study designs. Overall, PRP is considered a promising treatment for knee OA, particularly for pain relief and functional improvement.

PRP contains growth factors like platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-β), and vascular endothelial growth factor (VEGF). These factors are thought to help:

  • Reduce inflammation
  • Stimulate chondrocyte (cartilage cell) proliferation
  • Enhance matrix synthesis
  • Slow cartilage degradation

Here’s an overview of the current evidence:

Efficacy for Pain Relief and Function

Several meta-analyses have shown that PRP injections can provide significant improvements in pain relief and functional outcomes compared to placebo or hyaluronic acid (HA) injections:

  • American Journal of Sports Medicine (2017): A meta-analysis involving 14 randomized controlled trials (RCTs) showed that PRP injections led to significant improvements in pain and function at 6 months and 12 months compared to hyaluronic acid (HA) and saline injections. The benefits appeared more pronounced in younger patients and those with milder OA.
  • Clinical Orthopaedics and Related Research (2020): A meta-analysis of 30 RCTs concluded that PRP is more effective than saline or HA for reducing pain and improving function, particularly in mild to moderate knee OA, but results can vary based on PRP preparation methods and patient characteristics.
  • BMC Musculoskelet Disord (2021): Mclarnon and Heron reported superior outcomes of intraarticular PRP injections compared to corticosteroid injections for symptomatic knee OA. 
  • Arthroscopy (2021): Karasavvidis et al. reported that HA combined with PRP demonstrated greater improvement in pain, function, and stiffness compared to HA alone. 

Types of PRP

Variability in PRP Formulations: The clinical efficacy of PRP can depend on factors such as leukocyte concentration, platelet count, and activation methods. Leukocytes are known to influence wound healing and tissue repair. There is evidence that leukocyte-poor PRP (LP-PRP) may be more effective than leukocyte-rich PRP (LR-PRP) for knee OA, as high leukocyte concentrations may increase inflammation. Belk et al. took it further and assessed LP-PRP compared to leukocyte-rich PRP (LR-PRP) [28]. A statistically significant improvement in patient-reported outcome scores was demonstrated with PRP over HA, while LP-PRP was associated with significantly better International Knee Documentation Committee (IKDC) scores than LR-PRP.

 

Limitations and Considerations

  • Heterogeneity in Studies: The heterogeneity in study designs, PRP preparation methods, injection protocols, and outcome measures makes it difficult to draw uniform conclusions. Further standardization in PRP preparation and administration is needed.
  • Patient Selection: PRP appears to be more effective in patients with mild to moderate OA than in those with advanced OA (Kellgren-Lawrence grade IV), where its benefits might be limited.

Guidelines and Recommendations

  • Clinical Practice Guidelines: Some guidelines, such as those from the American Academy of Orthopaedic Surgeons (AAOS), are cautious and suggest that more high-quality evidence is needed before PRP can be universally recommended for knee OA. However, they acknowledge the potential benefits of PRP for certain patient populations.
  • Consensus Statements: The 2019 International Society for Cartilage Repair and Joint Preservation (ICRS) consensus statement recognized PRP as a treatment option for early knee OA, highlighting the need for personalized treatment plans based on patient characteristics and OA severity.