Three-month clinical outcomes and exploratory gait changes after intra-articular platelet-rich plasma for mild-to-moderate knee osteoarthritis: a prospective single-arm study

Background: Platelet-rich plasma (PRP) is used to treat knee osteoarthritis (KOA), yet its effects on gait are less clear than its effects on patient-reported symptoms. Methods: This prospective, single-center, single-arm pre–post study enrolled patients with symptomatic Kellgren–Lawrence grade I–II KOA. Participants received three intra-articular PRP injections at 7–14-day intervals. The primary outcome was the change in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score from baseline to 3 months. Secondary and exploratory outcomes included the International Knee Documentation Committee (IKDC) score, three-dimensional gait measures, PRP cellular composition, and safety. Results: Of 50 enrolled participants, 40 completed the 3-month follow-up. WOMAC total score decreased from 120.92 ± 22.16 to 73.45 ± 22.07 (mean change, −47.48; 95% CI, −54.57 to −40.38; P < 0.001; Cohen’s dz = −2.14), whereas IKDC score increased from 37.83 ± 3.14 to 44.12 ± 6.36 (mean change, 6.30; 95% CI, 4.31 to 8.29; P < 0.001; Cohen’s dz = 1.01). Among 11 exploratory gait outcomes, only the shoulder-hip to hip-knee angle remained significant after overall false discovery rate correction (q < 0.001). Maximum knee flexion remained significant only in a domain-specific sensitivity analysis. PRP showed approximately fivefold platelet enrichment and was classified as leukocyte-rich, red blood cell-containing PRP. No serious adverse events occurred. Conclusions: Three injections of leukocyte-rich, red blood cell-containing PRP were followed by short-term clinical improvement and a small number of gait changes in mild-to-moderate KOA. Controlled studies with longer follow-up are needed to determine whether these changes are attributable to PRP. Trial registration: Chinese Clinical Trial Registry, ChiCTR2500099663. Registered 27 March 2025, retrospectively registered.