Purpose: The main objective of our study was to evaluate the effectiveness of the injection of plasma rich in platelet-derived growth factors (PRGF) versus hyaluronic acid (HA) following arthroscopic surgery in patients diagnosed with internal derangement of the temporomandibular joint (TMJ) with osteoarthritis (OA). Materials and methods: A total of 100 patients were randomised into two study groups. Group A (n = 50) received an injection of PRGF, and Group B (n = 50) received an injection of HA. The mean age was 35.5 years (range 18-77 years), and 88% of the patients were women. The pain intensity (visual analogue scale) and the extent of maximum mouth opening before and after the procedure were statistically analysed. Results: Better results were observed in the group treated with PRGF, with a significant reduction in pain at 18 months, compared with HA treatment. Regarding mouth opening, an increase was observed in both groups, with no significant difference. Conclusions: The injection of PRGF following arthroscopy is more effective than the injection of HA with respect to pain in patients with advanced internal derangement of the TMJ. (C) 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.