What is one characteristic feature of diarthrodial joints?

Diarthrodial joints, also known as synovial joints, are characterized by their ability to allow for free movement between the bones they connect. This mobility is a result of their unique structure, which includes a joint capsule, synovial fluid, and articular cartilage. These features not only facilitate a wide range of motion but also help in providing lubrication and reducing friction during movement.

In contrast to the other types of joints listed, diarthrodial joints are specifically designed for mobility. Immovable joints, for example, are classified as synarthroses and allow little to no movement, primarily serving to stabilize bone structures in certain areas, such as the skull. Joints found in the skull are typically sutures, which are a type of immovable joint. Similarly, joints connected by cartilage refer more to synchrondroses or symphyses, which are classified as amphiarthrotic joints and allow limited movement, rather than the extensive range of motion permissible in diarthrodial joints. Thus, the designation of allowing free movement accurately describes one of the key characteristics of diarthrodial joints.