The objective od this study is to determine whether a specific muscle energy technique had an effect on the vertical range of opening of the mandible of the TMJ compared to therapeutic jaw exercises and non-intervention control group. Conclusions: Within the limitations of the study, the results support the hypothesis that the application of a specific osteopathic treatment, in this case MET and therapeutic jaw exercises can improve the range of opening in the TMJ. The results of this study provide a basis for further research as they present valuable outcomes for osteopaths treating jaw dysfunction. This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.