In which joint does the rotation phase of opening arthrokinematics occur?

The rotation phase of opening arthrokinematics occurs in the inferior mandibular joint, also known as the inferior compartment of the temporomandibular joint (TMJ). During the opening of the mouth, the first phase is primarily a rotational movement around the horizontal axis of the condyle within this inferior joint space. This movement allows for initial depression of the mandible, facilitating the optimal position for further translational movement which occurs later in the opening sequence.

The superior compartment of the TMJ, while also involved in the overall function of the joint, is primarily responsible for translational movements rather than the initial rotation. Additionally, the temporomandibular joint refers to the entire joint structure, which includes both the superior and inferior compartments. The maxillary joint is not involved in the opening of the mouth, as it refers to the junction between the maxilla and other craniofacial structures rather than the mandible. Understanding these specific roles of the compartments helps clarify why the inferior mandibular joint is where the rotation phase predominantly occurs.