What is the most likely cause of a patient's TMJ Disorder characterized by limited mandibular depression and altered mechanics?

• A. Ankylosis of the joint
• B. Anterior dislocation of the disc without relocation
• C. Muscle imbalance
• D. Chronic arthritis

Answer: (B)

The selection of anterior dislocation of the disc without relocation as the most likely cause of a patient's TMJ disorder characterized by limited mandibular depression and altered mechanics is rooted in the mechanics of the temporomandibular joint (TMJ) and the function of the articular disc.

In TMJ disorders, the disc plays a crucial role in facilitating smooth movement of the jaw. When the disc is displaced anteriorly and does not relocate, it can lead to a pronounced restriction in the ability to depress the jaw (open the mouth) fully due to improper alignment. This displacement often results in altered mechanics as the remaining structures of the joint try to compensate for the lack of smooth movement needed for normal mastication and other jaw functions. The inability of the disc to return to its correct position means that the condyle cannot move freely in relation to the disc, leading to limited range of motion and contributing to painful symptoms.

In the context of TMJ disorders, while conditions like ankylosis, muscle imbalance, and chronic arthritis can lead to similar symptoms, the specific presentation of limited mandibular depression and mechanical dysfunction aligns closely with an anterior dislocation of the disc without relocation. This condition directly impairs the normal kinematics of the TMJ, making it