Introduction: Hyaluronic acid (HA), a high-molecular-weight polysaccharide produced by type B synovial cells, is one of the main components of synovial fluid (SF). Within the joint cavity, HA plays a major role in joint lubrication and maintaining homeostasis. The molecular weight (MW) of hyaluronic acid (HA) in joints generally declines in inflammatory arthritis.

Objectives: Since inflammation exists in certain temporomandibular disorders (TMD), we measured the MW of HA in synovial fluid (SF) recovered from patients with TMD and compared it with that from normal controls. SF was obtained from patients with TMD (21 TMJs) and normal controls (5 TMJs). The MW of HA was measured using high-performance liquid chromatography.

Results: In the controls, the MW of HA in SF exceeded the detection limit, 3000 kDa. In contrast, 19 (90.5%) of 21 SF samples from patients showed a decreased MW of HA. The median MW of HA (1570 kDa) in TMD was significantly lower than in the controls ( p < .01).

Conclusions: This study clearly demonstrated that the MW of HA in SF from patients with ID and OA of the TMJ is decreased, probably due to free-radical depolymerisation of the HA chain or abnormal biosynthesis by the synovium, suggesting that degradation of HA have a critical role in the pathogenesis of degenerative changes of temporomandibular joint.

Conflict of interest: None declared.