Comparative efficacy of ultrasound-guided intra-articular injection of platelet-rich plasma (PRP), hydrolyzed type I collagen, and hyaluronic acid in patients with knee osteoarthritis: a randomized controlled trial

BACKGROUND: Intra-articular therapies are widely used for knee osteoarthritis (KOA), but direct comparisons between emerging biomaterials such as hydrolyzed collagen (HC) and established options like platelet-rich plasma (PRP) and hyaluronic acid (HA) are limited. OBJECTIVE: To compare the efficacy of intra-articular PRP, HC, and HA on pain, stiffness, and functional outcomes in KOA. METHODS: In this randomized, assessor- and statistician-blinded trial, 135 patients with Kellgren-Lawrence grade 2-3 KOA were assigned (1:1:1) to receive three ultrasound-guided Intra-articular injections of PRP, HC, or HA at two-week intervals. The primary outcome was change in WOMAC total score at 6 months. Secondary outcomes included WOMAC subscales, VAS pain, and the Lequesne Index. RESULTS: One hundred twenty-six patients completed follow-up. All groups showed significant improvements (p < 0.001). HA demonstrated greater improvements in some outcome measures at 1 month. PRP and HC demonstrated more sustained improvements than HA during 1 to 6 months follow-ups, although statistically significant between-group differences were limited to selected outcomes. No serious adverse events occurred. CONCLUSION: Intra-articular PRP, HC, and HA improved outcomes in mild to moderate knee OA; PRP and HC showed a trend toward more sustained benefits during 1 to 6 months. Longer-term trials are necessary to confirm these findings.