Background: Transverse mandibular discrepancies are often overlooked during orthodontic treatment. MSDO is a treatment to address this issue, but much debate exists over the long-term implications on the temporomandibular joint (TMJ). Few studies have sample sizes sufficient to draw clear conclusions about the impact of MSDO on TMJ health. Materials and Methods: This study evaluated private practice records including 49 MSDO patients and 57 traditionally-treated controls. The subjects were assessed by TMD exams that evaluated jaw pain and discomfort using visual analog scales, range of motion for opening, right and left lateral, and protrusive movements, and the presence of clenching, bruxism, clicking, crepitus, and pain on TMJ and muscle palpation. Results: No significant changes between the groups were noted during treatment or follow-up. Conclusions: Compared to controls, MSDO patients did not experience any increase in TMD symptoms. Distraction and control patients were not significantly different in any of the categories.