Intra-Articular Leukocyte-Poor Platelet-Rich Plasma Injections for Japanese Patients With Osteoarthritis of the Knee: A Three-Year Observational Retrospective Study After Phase 1 and Phase 2a Trials

Background: We have previously confirmed the safety and feasibility of intra-articular (IA) platelet-rich plasma (PRP) injections in Japanese patients with osteoarthritis (OA) of the knee. This study aimed to investigate the clinical and radiological outcomes in patients who were followed up for three years. Methods: Nine patients were evaluated in this observational study. All the patients were women with a mean age of 60.6 years. PRP was prepared by single centrifugation and classified as leukocyte-poor (LP)-PRP, and was administered via three IA injections at weekly intervals. Patients were evaluated at baseline and final follow-up using the Kellgren-Lawrence (KL) grade and the Japanese Orthopedics Association (JOA) score. The need for additional treatment was also investigated at the final follow-up. Results: At a mean follow-up of three years, the JOA score improved from 75 points (p) to 83.8 p. The sub-categorical scores changed as follows: gait, 23.1-26.9 p; stairs, 12.5-17.5 p; range of motion, 30-30 p; and swelling, 9.4-10 p. While the KL grade was maintained in six patients, it progressed in two patients from I to II and II to III, respectively. Two patients received additional treatment at the final follow-up. Conclusions: At the final follow-up, the functional knee score, especially gait and the ability to go up and down the stairs, improved in six out of eight patients without additional treatment. These results suggest that LP-PRP injections produced safe outcomes without OA-worsening in most patients at three-year follow-up.