Algo-dysfunctional syndrome (ADS) of the temporo-mandibular joint (TMJ) is frequently encountered and, since its clinical expression is extremely polymorphic, it is often misdiagnosed. As there are many causes for ADS, even in a single patient, in line with the most recent interpretations found in the literature, an attempt was made to determine how important the lack of muscular coordination is in the onset of clinical symptoms. The study was conducted on 48 patients (32 females, 16 males, age range 17-68 years, average age 41.7 years) with ADS, clinically diagnosed according to the criteria defined by Rendell et al. The patients belonged to three distinct groups: -Group 1: patients with ADS of articular origin (9 cases); -Group 2: patients with ADS of dental and/or periodontal origin (18 cases); -Group 3: patients with ADS for which there was no apparent cause (21 cases). All patients were treated with a rehabilitation protocol aimed at eliminating the muscle spasm and restoring correct coordination. The results obtained showed that conservative treatment to resolve the muscle spasm gave positive results in 69% of the cases. The patients with concomitant articular pathology proved the least responsive to treatment. It was, therefore, considered likely that the main cause for clinical expression of this pathology is the muscle spasm itself. On this basis it can be concluded that muscular rehabilitation of the TMJ is valid in the treatment of ADS as it has proved able to break the vicious cycle of symptoms at the base of this pathology.