Glucosamine supplementation in the treatment of temporomandibular joint disorders: a systematic review and meta-analysis

Background: Glucosamine has been proposed as a therapeutic option for temporomandibular disorders (TMD), particularly temporomandibular joint osteoarthritis (TMJ OA), but its effectiveness and safety remain uncertain. Objective: To evaluate the benefits and harms of oral glucosamine supplementation in patients with TMJ OA and other/unspecified TMD. Methods: A systematic review was conducted in PubMed/MEDLINE, CENTRAL, Scopus, and Embase through October 8, 2025. Randomized controlled trials (RCTs) evaluating oral glucosamine supplementation in patients with any type of TMD, including TMJ OA, were selected. Meta-analyses were performed using random-effects models, and the GRADE methodology was applied to assess the certainty of the evidence. Results: Seven RCTs were included. In patients with TMJ OA, compared with placebo, glucosamine may not result in a clinically important reduction in pain at ≤3 months (MD -1.58 mm; 95% CI -5.98 to 2.83; low certainty) and probably does not provide a clinically important reduction at 6 months despite statistical significance (MD -7.02 mm; 95% CI -11.95 to -2.09; moderate certainty). Glucosamine improved quality of life at 12 months (MD -4.14; 95% CI -6.41 to -1.87; high certainty). Compared with active controls, the effect on pain was uncertain, although quality of life may improve at 3 months. In patients with other/unspecified TMD, glucosamine may not meaningfully reduce pain but may increase maximum pain-free mandibular opening at 3 months. Evidence regarding adverse and serious adverse events was very uncertain across comparisons. Conclusion: Oral glucosamine does not provide a clinically important reduction in pain in TMJ OA or other/unspecified TMD but may improve quality of life in TMJ OA. Evidence for functional outcomes and adverse events remains uncertain, highlighting the need for high-quality randomized trials. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD42024531131, identifier CRD42024531131.