BACKGROUND: Temporomandibular joint (TMJ) arthralgia is a painful condition assumed to be associated with local inflammation. OBJECTIVE: The objective of the present study was to determine the efficacy for reducing pain of a single-dose intra-articular (IA) injection of methylprednisolone to the TMJ. The hypothesis was that methylprednisolone would effectively reduce TMJ pain. METHODS: This randomised, double-blind, parallel-group, multicentre, controlled study included visits for enrolment, treatment and 4-week follow-up. The study included patients 18 years and older who had been diagnosed with unilateral TMJ arthralgia. All participants were randomly assigned to receive 1 mL IA injections of methylprednisolone or saline. The primary outcome was change in recorded pain intensity on a visual analogue scale (VAS) at maximum jaw opening, analysed in the per protocol population. RESULTS: In total, 54 patients were randomly assigned to single-dose IA injections with methylprednisolone (n = 27) or saline (n = 27). Between baseline and the 4-week follow-up, VAS-rated pain intensity at maximum jaw opening decreased from a mean of 61.0 (95% confidence interval [CI]: 50.1; 70.7) to 33.9 (95% CI: 21.6; 46.2) in the methylprednisolone group and from 59.6 (95% CI: 50.7; 65.9) to 33.9 (95% CI: 23.8; 43.9) in the saline group. The between-group difference was not significant (P = 0.812). Treatment-related adverse events were doubled in the methylprednisolone group. CONCLUSION: Methylprednisolone provided no additional benefit for reducing pain, but caused more harm compared with saline following a single-dose IA injection in patients with TMJ arthralgia.