Preliminary Clinical Outcomes of Biotherapy Combined With Rehabilitation for the Treatment of Knee Osteoarthritis: A Retrospective Observational Study

BACKGROUND: Knee osteoarthritis (KOA) is a common musculoskeletal condition that markedly reduces patients' quality of life and places an increasing burden on healthcare systems. Biotherapy has anti-inflammatory and tissue-reparative effects but does not adequately address KOA-related biomechanical or functional impairments. In contrast, rehabilitation improves muscle function and gait mechanics. Although combining these approaches may improve outcomes in patients with KOA, related clinical evidence remains limited. OBJECTIVE: This study aimed to preliminarily investigate the combined effects of platelet-derived factor concentrate-freeze-dried (PFC-FD) injection therapy and rehabilitation in patients with KOA at one and three months following injection. METHODS: This retrospective observational study analyzed data of 17 patients with KOA who underwent three sessions of freeze-dried platelet-derived factor concentrate injections, followed by at least three sessions of standardized rehabilitation. Patient-reported outcomes were assessed at baseline and one month and three months after treatment, using the Japanese version of the Knee Injury and Osteoarthritis Outcome Score (J-KOOS). The primary outcome was response rate, which was defined according to the Outcome Measures in Rheumatology-Osteoarthritis Research Society International criteria. Longitudinal changes in J-KOOS scores were analyzed using a linear mixed-effects model. RESULTS: Among the 17 patients assessed (median age, 68 years; 71% women), 9 (52.9%) met the responder criteria at one month and 12 (70.6%) at three months. The response rate and effect sizes for the functional subscales (e.g., quality of life: d = 1.62) were comparatively higher than those typically reported for PFC-FD injection alone. CONCLUSION: The combination of PFC-FD injection and rehabilitation showed potentially favorable clinical outcomes, particularly for improving physical function and quality of life. Given the preliminary and non-controlled nature of this study, these findings should be interpreted with caution. Future controlled studies are warranted to confirm whether rehabilitation augments the clinical benefits of injection therapy.