Injectable Hydrogels for the Treatment of Temporomandibular Joint Osteoarthritis: From Tissue-Engineering Scaffolds to Joint Lubricants and Mechanical Buffers.

Introduction/Objectives: Temporomandibular joint osteoarthritis (TMJOA) causes pain, mandibular dysfunction, fibrocartilage degradation, and synovial inflammation. Current therapies are mainly palliative and limited by rapid intra-articular clearance and insufficient disease-modifying effects. This review summarizes injectable hydrogels for TMJOA as regenerative scaffolds, drug delivery systems, joint lubricants, and mechanical buffers. Methods: Relevant studies were identified from PubMed/MEDLINE, Web of Science and Google Scholar using terms related to TMJOA, injectable hydrogels, intra-articular delivery, tissue engineering, cartilage repair, lubrication, viscosupplementation and mechanical buffering. Studies were selected if they addressed hydrogel design, biological function, mechanical performance, biosafety or translational evaluation. Results: Injectable hydrogels have been investigated mainly as bioactive regenerative scaffolds and acellular functional biomaterials. Bioactive systems may regulate inflammation and oxidative stress, deliver cells, exosomes, drugs or growth factors, and support fibrocartilage repair. Acellular systems primarily aim to improve intra-articular retention, lubrication, viscoelastic adaptation and mechanical buffering. However, current evidence remains largely preclinical, with limited validation of long-term residence, degradation behavior, TMJ-specific mechanical performance, repeat dosing, biosafety and functional outcomes. Conclusions: Injectable hydrogels represent promising multifunctional platforms for TMJOA treatment. Cell-, exosome-, and growth factor-loaded systems show regenerative potential but face manufacturing, safety, regulatory, and long-term validation challenges. Acellular multifunctional hydrogels may be more feasible for near-term translation. Clinical Significance: Injectable hydrogels may provide minimally invasive, locally sustained treatment for TMJOA by integrating symptom control, microenvironment modulation, and mechanical adaptation.