The digastric muscle, also referred to as the digastricus, is a small muscle situated under the jaw. The primary function of this muscle is to elevate the hyoid bone – a small, horseshoe shaped bone located between the thyroid cartilage and chin. By elevating the hyoid bone, the digastric muscle depresses or lowers the mandible, helping to open the mouth and also assisting in swallowing.

The name “disgastric” is indicative of the muscle’s double-bellied structure, though other muscles in the human body also possess two or more structural bellies. The anterior belly, being the smaller of the two structures, is located on the lower border of the mandible. The larger posterior belly is located on the inferior surface of the skull, on the medial surface of the mastoid process on the temporal bone. The two bellies are joined by an intermediate tendon.

Locating your digastric muscle can be tricky, but you may be able to feel the anterior belly contract by placing your finger under your chin and trying to open your mouth against your finger’s gentle resistance. At the same time, place another finger on the mastoid process – the large, round bony bump behind your earlobe. The contractions you feel in both areas are the anterior and posterior bellies of the digastric muscle.

Pain or discomfort in the digastric muscle may be related to muscle tears and sprains or injuries due to overuse. Some conditions which may affect the digastric muscle include myopathy, atrophy, infectious myositis, lacerations, contusions or neuromuscular diseases. Temporomandibular joint disorder (TMJ) is a general term used to describe acute or chronic pain in the jaw or surrounding face muscles, typically caused by muscle overuse or repetitive jaw-clenching and teeth grinding. Treatment for conditions of the digastric muscle typically entails pain-relief medications or muscle repair surgery. TMJ cases may require oral splints or dental surgery to minimize impact on the digastric muscle caused by the teeth.