Rapid pain relief after intra-articular injection of adipose-derived stromal vascular fraction in patients with knee osteoarthritis: a retrospective cohort study

Background Intra-articular injection of adipose-derived stromal vascular fraction (SVF) has emerged as a promising regenerative treatment for knee osteoarthritis (OA) because of its heterogeneous cellular composition and potent anti-inflammatory paracrine effects. However, the timing of pain relief and the influence of SVF cell dose on early clinical outcomes remain incompletely defined. Methods This retrospective study included 146 patients (217 knees) with Kellgren–Lawrence (K–L) grade II–IV knee OA who underwent intra-articular injection of autologous SVF and completed a minimum follow-up of 1 year. Pain was assessed using the visual analog scale (VAS), and patients reported the time to perceived pain improvement after treatment. Radiographic severity was evaluated using the K–L grading system. Correlation analyses were performed to assess associations between pain-related outcomes, SVF cell number, and radiographic severity. Results VAS scores improved significantly from baseline to the final follow-up (P < 0.01). Patients reported perceived pain improvement at a mean of 18.9 ± 14.5 days after SVF injection. The mean injected dose was 7.4 × 10⁷ total SVF cells per knee, including approximately 7.0 × 10⁶ stromal cells. Higher SVF cell numbers were significantly associated with greater pain improvement and lower VAS scores at final follow-up (P < 0.001 for both). Radiographic severity was not significantly correlated with pain outcomes. No clinically relevant adverse events were observed. Conclusions Intra-articular injection of high-dose autologous SVF was associated with rapid and clinically meaningful pain relief, with symptom improvement occurring within approximately 3 weeks after treatment. The dose-dependent association and the lack of correlation with radiographic severity suggest that early pain relief is primarily mediated by the anti-inflammatory and paracrine effects of SVF rather than immediate structural cartilage regeneration.