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Why must both temporomandibular joints move together when the lower jaw moves?

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Medical illustration of a human knee joint in a parasagittal section just lateral to the midline, labeling ligaments, cartilage, meniscus, patella, synovial structures, and surrounding muscles and fat pads. — joint The ligaments and cartilage in a knee joint.

The temporomandibular joints (TMJs) must function in unison because they are connected by a single, solid bone: the mandible.

In humans, the mandible is a single, fused structure that forms a horizontal arch. Because the two temporomandibular joints articulate with the skull at the rear ends of this single bone, any movement of the lower jaw—whether opening, closing, protruding, retracting, or moving laterally—necessarily involves both joints simultaneously. If the joints did not move in coordination, the structural integrity of the mandible would be compromised, as it cannot bend or move independently on one side without affecting the other.12

This complex movement involves more than a simple hinge action; as the jaw opens, the ends of the mandible rotate and then slide forward along the temporal bones, requiring precise synchronization between both sides to maintain proper jaw function.2