San Diego TMJ
The temporomandibular joint
This media is for information purposes ONLY and are NOT intended to replace professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition.
The temporomandibular joint — the TMJ – is the joint between the lower jawbone – the mandible – and the temporal bone of the skull. The TMJ is responsible for jaw movement and is the most used joint in the body. The TMJ is essentially the articulation between the condyle of the mandible and the mandibular fossa – a socket in the temporal bone. The unique feature of the TMJ is the articular disc – a flexible and elastic cartilage that serves as a cushion between the two bone surfaces.
The disc lacks nerve endings and blood vessels in its center and therefore is insensitive to pain. Anteriorly it attaches to lateral pterygoid muscle – a muscle of chewing. Posteriorly it continues as retrodiscal tissue fully supplied with blood vessels and nerves.
The mandible is the only bone that moves when the mouth opens. The first 20 mm opening involves only a rotational movement of the condyle within the socket. For the mouth to open wider, the condyle and the disc have to move out of the socket, forward and down the articular eminence, a convex bone surface located anteriorly to the socket . This movement is called translation.
The most common disorder of the TMJ is disc displacement, and in most of the cases, the disc is dislocated anteriorly. As the disc moves forward, the retrodiscal tissue is pulled in between the two bones. This can be very painful as this tissue is fully vascular and innervated, unlike the disc. The movements made by chewing or even talking cause a chronic bruise to the tissue resulting in inflammation and pain.