Increased baseline depression symptomology is associated with worse patient-reported pain and function following PRP for knee Osteoarthritis (OA): a retrospective longitudinal study

Abstract Objective Platelet-rich plasma (PRP) is increasingly used to treat knee osteoarthritis (KOA), but variability in reported outcomes has limited broader adoption. Patient-specific psychosocial factors, including depressive symptoms, may be associated with patient-reported outcomes following treatment. This study evaluated whether baseline depressive symptom severity affects pain and functional outcomes following PRP injections for KOA. Methods A retrospective analysis of prospectively collected registry data was conducted among patients receiving PRP injections for symptomatic KOA. Depressive symptoms were assessed using the Patient Health Questionnaire–4 (PHQ-4) and categorized as none (0–2), mild (3–5), or moderate-to-severe (6–12). The primary outcome was pain measured by the Numeric Rating Scale (NRS), and the secondary outcome was function measured by the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR). Outcomes were recorded at baseline and 1, 3, 6, 12, 18, and 24 months. Mixed-effects repeated-measures models evaluated outcome trajectories. Results A total of 1206 patients were included (mean age 63 years; mean BMI 28.2 kg/m²; 57% female). Baseline PHQ-4 category significantly influenced overall pain scores ( P < 0.0001 for the main effect), with a significant PHQ-4-by- time interaction over 24 months ( P = 0.046). Patients without depressive symptoms reported lower overall pain (mean NRS 3.4; 95% CI 2.8–4.0) compared with mild (4.3; 95% CI 3.6–4.9) and moderate-to-severe groups (4.4; 95% CI 3.6–5.2). Time-averaged KOOS-JR scores were also higher in patients without depressive symptoms (67.8 vs. 61.7 vs. 60.5; P < 0.0001). Conclusion Baseline depressive symptoms are associated with greater patient-reported pain burden and worse functional outcomes following PRP treatment for KOA despite overall similar improvement in both groups. Whether this reflects a diminished response to PRP specifically or the broader relationship between depression and musculoskeletal pain needs to be further studied.