Masseter muscles are our muscles of mastication, or chewing. If you feel where your jawline hinges on either side of your skull, there’s a right angle. “If you bite down, you can see and feel the prominence or bulge there — that’s the muscle,” Dr. Doft explains. If you have TMJ, you might have other symptoms that relate to your masseter muscles. Robert Merrill, DDS, clinical professor and residency director for oral facial pain at the UCLA School of Dentistry tells R29: “This would include some jaw muscle tenderness, clicking, or other noises during jaw movement and joint tenderness,” he says.