Comparative Effectiveness of Intra-Articular Nanofat and Platelet-Rich Plasma Injections in Pain Relief and Functional Improvement for Unilateral Knee Osteoarthritis: A Retrospective Cohort Study.

BACKGROUND: Knee osteoarthritis (OA) is a leading cause of chronic pain and disability. Regenerative therapies such as intra-articular injections of platelet-rich plasma (PRP) and nanofat (and adipose-derived stromal vascular fraction) have emerged as promising treatment options, but comparative evidence on their effectiveness remains limited. OBJECTIVE: To compare the efficacy of intra-articular PRP injections to that of nanofat injections for pain relief and functional improvement in patients with predominantly unilateral knee OA over a 6-month follow-up. STUDY DESIGN: A retrospective cohort study. METHODS: In this retrospective cohort study, data from 149 patients treated between July 2023 and August 2025 at a tertiary pain clinic in India were analyzed. Ninety-two patients received intra-articular PRP injections, and 57 received intra-articular nanofat injections. The patients' pain was assessed on the Numeric Pain Rating Scale (NPRS) and their functioning with the 6-minute walk test (6MWT) via the Accupedo mobile app. Group differences were adjusted for baseline pain and varus deformity using a repeated measures ANCOVA. Logistic regression identified predictors of ≥ 50% pain relief. RESULTS: Both treatments reduced pain over 6 months, but the 6MWD scores showed that nanofat was associated with greater and more sustained pain relief (P < 0.01) and functional improvement than was PRP (P = 0.006). The odds of achieving ≥ 50% pain relief were higher in the nanofat group (adjusted OR 2.05, 95% CI 0.92 to 4.58, P = 0.078), though this finding did not reach statistical significance. Varus deformity ≥ 5° lowered the odds of significant pain relief (adjusted OR 0.44, 95% CI 0.19 to 1.02, P = 0.056). LIMITATIONS: The retrospective design, lack of randomization, attrition in the PRP group, use of baseline observation carried forward (BOCF), and relatively short follow-up period limit causal inference and long-term generalizability. CONCLUSIONS: Nanofat injections provide greater, longer-lasting pain relief and functional benefits for unilateral knee OA than PRP injections do, although larger randomized studies are needed to confirm these findings. Baseline varus deformity may influence treatment outcomes.