You may not have heard of it, but you use it hundreds of times every day. It is the Temporo-Mandibular Joint (TMJ), the joint where the mandible (the lower jaw) joins the temporal bone of the skull, immediately in front of the ear on each side of your head. A small disc of cartilage separates the bones, much like in the knee joint, so that the mandible may slide easily; each time you chew you move it. But you also move it every time you talk and each time you swallow (every three minutes or so). It is, therefore, one of the most frequently used of all joints of the body and one of the most complex. You can locate this joint by putting your finger on the triangular structure in front of your ear. Then move your finger just slightly forward and press firmly while you open your jaw all the way and shut it. The motion you feel is the TMJ. You can also feel the joint motion in your ear canal. These maneuvers can cause considerable discomfort to a patient who is having TMJ trouble, and physicians use these maneuvers with patients for diagnosis.