RESUMO
PURPOSE: To assess the noninferiority of a single platelet-rich plasma (PRP) injection compared with hyaluronic acid (HA), to alleviate pain and enhance functional capacity in knee osteoarthritis, and identify biological characteristics of PRP that may affect their efficacy. METHODS: Fifty-four patients with symptomatic knee osteoarthritis received a single injection of either PRP (26 patients) or HA (28 patients). They were assessed at baseline and at 1, 3, and 6 months. The primary endpoint was the change in Western Ontario and McMaster Universities Arthritis Index (WOMAC) score at 3 months, and secondary endpoints were responders' rate (improvement of at least 5 points or 40% of WOMAC total score at 3 months) of pain evaluation and patient's subjective satisfaction. Cell counts and the contents of vascular endothelial growth factor (VEGF), platelet-derived growth factor-AB (PDGF-AB), transforming growth factor beta 1 (TGF-ß1) content of injected PRP were assessed to analyze their relationship with clinical outcome. RESULTS: Both treatments proved their improvement in knee functional status and symptom relief, with a significant decrease observed at 1 month on all scores except for pain VAS in PRP group and WOMAC function score in the HA group. No difference between groups regarding WOMAC and VAS scores was observed. A higher percentage of responders was observed in the PRP group (72.7%) than in the HA group (45.8%) without significance (P = .064). The quantity of injected PDGF-AB and TGF-ß1 correlated with the change in WOMAC scores at 3 months and was lower in responders than in nonresponders (P = .009 and P = .003, respectively). CONCLUSIONS: Current results indicated that a single injection of very pure PRP offers a significant clinical improvement in the management of knee osteoarthritis, equivalent to a single HA injection in this patient population. Moreover, a significant correlation between the doses of TGF-ß1 and PDGF-AB and the worsening of WOMAC score 3 months after the procedure was found. LEVEL OF EVIDENCE: Level II, randomized double blind controlled trial.