Which type of synovial joint allows movement in one direction?

A hinge joint is indeed the correct choice for this question. This type of synovial joint allows movement primarily in one direction, similar to the way a door opens and closes. The structure of a hinge joint includes two articulating surfaces: one is concave, while the other is convex. This configuration permits flexion and extension movements, allowing body parts, such as the elbow and knee, to move forwards and backwards.

Understanding the functional characteristics of different joints can highlight why a hinge joint is categorized this way. For instance, ball and socket joints, like the hip or shoulder, offer a greater range of motion, allowing movement in multiple directions, including rotation. Condyloid joints permit movement between two axes, as seen in the wrist, enabling both flexion/extension and lateral movements. Pivot joints, such as those found in the neck, allow rotation around a single axis but do not support the same linear motion as hinge joints.

Therefore, the unique structure and movement capabilities of the hinge joint clearly define its ability to facilitate movement primarily in one direction.