The temporomandibular joint has glide and hinge motions in its upper and lower portions, respectively. Grinding or chewing consists primarily of gliding movements in the upper compartments.
Range of motion is three-fold: ask the patient to demonstrate opening and closing, protrusion and retraction (by jutting the jaw forward), and lateral, or side-to-side, motion. Normally as the mouth is opened wide, three fingers can be inserted between incisors. During normal protrusion of the jaw, the bottom teeth can be placed in front of the upper teeth.
Dislocation of the TMJ may be seen in trauma.
Swelling, tenderness, and decreased range of motion suggest arthritis.
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