Abstract
BACKGROUND: Monthly, ultrasound-guided intra-articular injections of leukocyte-poor platelet-rich plasma (ACP®) are widely used for knee osteoarthritis (KOA), but optimal dosing and cumulative exposure remain unclear. METHODS: We retrospectively analyzed prospectively planned ACP treatments at a single clinic. Knees with KL1-4 received fixed per-knee doses (3 mL [3A] or 6 mL [6A]) monthly up to six sessions. Primary outcome was VAS pain; secondary outcomes were KOOS (Pain/ADL/QoL), OMERACT-OARSI response, MOAKS-BML, and joint effusion (JF). ANCOVA for ΔVAS at 12 months adjusted for baseline VAS and prespecified covariates; longitudinal mixed-effects models and segmented regression assessed dose-response and breakpoint. RESULTS: Pain improved at 12 months (n = 115) and was maintained at 24 months (n = 67). Segmented regression identified a dose-response plateau around the 4th injection. The 6 mL regimen showed no robust adjusted advantage over 3 mL at 12 months. KOOS domains and OMERACT-OARSI responder rates improved at 12 months and persisted at 24 months. MOAKS-BML decreased from 12 to 24 months; JF tended to decline. No serious adverse events related to ACP injections were documented. CONCLUSIONS: Under a fixed monthly protocol mirroring our LR-PRP schedule, ACP (LP-PRP) produced clinically meaningful improvements across KL1-4 with a practical evaluation horizon through the 4th injection and no clear per-session volume benefit of 6 mL over 3 mL. Prospective randomization of dose within a monthly-multiple framework is warranted.