Hyaluronic Acid Molecular Weight in the Minimally Invasive Management of Temporomandibular Disorders: A Scoping Review

Background/Objectives: This scoping review mapped how hyaluronic acid (HA) molecular weight has been defined and investigated in direct clinical comparisons for temporomandibular disorders (TMDs), including formulations, populations, procedures, outcomes, and methodological limitations. Methods: Final searches and selection were completed on 9 September 2026 using PubMed, BASE, CENTRAL, and Europe PMC. Prospective human studies comparing different intra-articular HA preparations under the same procedural protocol were eligible, including matched comparisons within multi-arm studies. Two reviewers independently screened and charted the evidence. Findings were synthesized descriptively without meta-analysis or formal risk-of-bias assessment. The protocol was registered in OSF (osf.io/sc8wv). Results: Five reports were included: three quasi-randomized trials and two prospective studies with sequential or unreported allocation between HA formulations. Four reported efficacy comparisons; one contributed safety data only after swelling and marked pain in 2 of 5 recipients prompted discontinuation of a high-molecular-weight arm. Molecular-weight categories overlapped across reports, formulation characteristics were incompletely reported, and protocols varied from one to five injections with differing use of arthrocentesis. Comparative follow-up ranged from 3 to 12 months. No eligible efficacy comparison detected a statistically significant difference, but small samples, allocation limitations, and incomplete subgroup reporting restricted interpretation. Conclusions: The evidence map identifies inconsistent formulation classification, procedural heterogeneity, and deficiencies in outcome and safety reporting as barriers to interpretation. It does not establish equivalence, superiority, or comparative safety of molecular-weight categories and provides specific priorities for future studies.