Ninety-six patients with medial compartment knee osteoarthritis were randomized to receive a opening-wedge high tibial osteotomy with a platelet-rich plasma injection (PRP) (n=48) or without any additional treatment (n=48). Outcomes of interest included pain on a Visual Analog Scale (VAS), the Western Ontario and McMaster University Osteoarthritis Index, Lysholm score, minimum medial joint space width, and mechanical alignment, assessed up to 24 months post-operation. Results revealed a significantly improved minimum medial joint space width in the PRP group. Moreover, a higher proportion of patients in the PRP group exceeded the minimum clinically important difference in the first year for Lysholm and WOMAC scores; this was particularly pronounced in the first 6 months of follow-up.