Hygiene Atlas

Atlas · Plate I · Head and Neck Anatomy · 02

Temporomandibular joint

The TMJ joins the mandibular condyle to the articular fossa and eminence of the temporal bone. Its disc splits the joint into a lower space that hinges and an upper space that glides, so opening starts with rotation and then the condyle slides forward. Normal opening is about 40-50 mm, and a click on opening usually means the disc sits too far forward.

High-yield facts · 7

  1. The TMJ is a ginglymoarthrodial joint: it both hinges (rotates) and glides (translates).T4
  2. The articular disc divides the joint into an upper (gliding/translation) and a lower (hinge/rotation) space.T4
  3. The joint is formed by the mandibular condyle and the articular fossa and eminence of the temporal bone.T4
  4. The lateral pterygoid inserts partly on the disc and the condylar neck and pulls the condyle forward.T4
  5. Normal maximum opening is about 40-50 mm measured between incisal edges; under about 35-40 mm suggests limitation (trismus).T2
  6. Clicking on opening usually reflects anterior disc displacement with reduction.T4
  7. Dislocation happens when the condyle moves anterior to the articular eminence and locks open.T4

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.