Is proprioception affected in those with persistent intra-articular temporomandibular disorders? A cross-sectional study exploring joint position sense and force sense of the jaw.

BACKGROUND: Proprioception is an important component of normal jaw function, although to date it is unknown if and how proprioception is affected in those with intra-articular temporomandibular disorders (IA-TMDs). This challenges effective management of this subgroup. OBJECTIVES: Determine whether differences in local joint position sense and force sense exist between individuals with IA-TMD and those without a jaw problem. DESIGN: Cross-sectional study. METHOD: Sixty age and sex matched participants were recruited (n = 30 IA-TMD, n = 30 healthy controls). Temporomandibular joint position sense was tested to one target (50% of maximal mouth opening) using a ruler. Temporomandibular force sense was tested to two targets (50% and 70% of maximal molar pain-free bite force) using a bite sensor. Constant, absolute and variable errors were calculated for each outcome and compared between groups using p-values and 95% confidence intervals for effect size (d). RESULTS: Significantly greater degrees of constant, absolute and variable error were seen for force sense testing at the 50% target (p < 0.05). No statistically significant difference was observed between groups for joint position sense, or for constant or variable force sense error at the 70% target (p > 0.05). Despite this, all joint position sense and force sense measures demonstrated possible clinical significance (upper limits 95% CI d >/= 0.5). CONCLUSIONS: Force sense, particularly at lower levels, appears impaired in those with IA-TMD. Joint position sense and force sense at higher levels appear less affected, although may still be important to consider in the management of IA-TMD in some patients.