Ankylosis forming between the zygomatic arch and the coronoid process is a rarely encountered pathological extracapsular ankylosis. Its treatment protocol consists of surgical removal of the coronoid process with the ankylotic mass and jaw opening-closing exercises after surgery. Myositis ossificans (MO) is a self-limiting, benign ossifying lesion. It affects all types of soft tissues including subcutaneous adipose tissue, muscles, tendons and nerves. It is most frequently found in the muscle as a solitary lesion. The clinical appearance of MO is generally in the form of a mass characterized with an ossified soft tissue. When it develops alone, cross-sectional imaging might not be specific, and it may appear similar to worse etiologies. It is suggested multiple imaging modalities should be used in the assessment of a suspicious soft tissue mass. MO is a benign self-limiting disease. In this case report, in the radiographic examination of a 41-year-old female patient, ankylosis between the left coronoid process and the zygomatic bone accompanied by possible MO in the left medial pterygoid muscle was observed. Resection of the coronoid process with the ipsilateral route, resection of the ankylotic mass with the hemicoronal approach and resection of the contralateral coronoid process with the intraoral approach were performed, but the ossified formation in the medial pterygoid muscle was not touched.