Natural course of acute closed lock of the temporomandibular joint.

To clarify the features of acute closed lock of the temporomandibular joint we compared the clinical condition of patients with acute and chronic closed lock, and investigated the natural history of acute closed lock. Forty patients with unilateral acute closed lock who were given no treatment and 40 patients with unilateral chronic closed lock were enrolled in the study. The duration of locking in those with acute closed lock ranged from 1 to 7 days, and that of those with chronic closed lock from 3 to 4 months. Differences between the groups in sex, age, maximum mouth opening, and joint pain were analysed. In those with acute closed lock who had had no treatment, maximum mouth opening and joint pain were measured at the initial visit and after 2, 4, 8, and 12 weeks. The number of dysfunctional joints was counted during each period and the natural course of the acute closed lock investigated. There were more women and older patients among those with chronic, than among those with acute, closed lock. We found no significant differences in the symptoms in the two groups. After 2 weeks of allowing the acute closed lock to take its natural course only 15 of the 40 had not resolved successfully, and after 12 weeks of taking its natural course only 2 had been unsuccessful. The number of joints that did not resolve successfully decreased progressively over time. Any treatment for acute closed lock should be easier and more effective than that of following its natural course.