Platelet-Rich Plasma for Knee Osteoarthritis and Patient-Reported Outcomes: A Large Retrospective Analysis

Background: Platelet-rich plasma (PRP) is used increasingly to treat knee osteoarthritis (OA). This study aimed to describe PRP use for knee OA and identify patient- and treatment-specific factors associated with clinical outcomes. Hypothesis: Patients with knee OA undergoing intra-articular PRP injections would demonstrate improvement in pain, function, and symptoms over time, with outcomes varying by patient and treatment characteristics. Study Design: Retrospective cohort study. Level of Evidence: Level 3. Methods: A total of 743 patients with knee OA were treated with intra-articular PRP injections. Outcomes were assessed using the Numeric Rating Scale (NRS, 0-100, higher scores indicating greater pain) and the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR). Change in patient-reported outcome measure (PROM) scores from baseline and achievement of patient acceptable symptom state (PASS) were measured. Repeated-measures mixed models evaluated outcomes at baseline, 6 months, and 1 year using an all-response analysis (391 patients for Pain NRS; 400 for KOOS-JR). Results: PRP injections were associated with improvement in pain, function, and symptom state. Pain NRS improved from 39.2 at baseline to 27.2 at 6 months and 22.4 at 1 year (both P < 0.001), while KOOS-JR improved from 60.7 to 68.5 and 69.1 (both P < 0.001), with similar findings in the complete-case cohort. When stratified by radiographic severity, patients with Kellgren-Lawrence (KL) grades 1 to 3 improved in both outcomes at 6 months and 1 year, while patients with KL grade 4 improved in Pain NRS at 1 year ( P < 0.001) and KOOS-JR at 6 months ( P = 0.01) and 1 year ( P = 0.001). PASS achievement rates increased over time for both pain and function. Conclusion: Intra-articular PRP injections were associated with improvements in pain, function, and symptoms in patients with knee OA. Differences between complete-case and all-response analyses suggest that follow-up patterns may influence estimated treatment response. Clinical Relevance: These findings describe patient-reported outcomes after intra-articular PRP injection for knee OA. Because this study lacked a control group, findings should not be interpreted as evidence that PRP caused the observed improvements.