Final answer:
The range of motion of a movable joint is expressed in degrees, as it involves angular motion such as flexion and extension. Highly mobile joints like the shoulder offer a wide range of motion but are less stable compared to joints like the carpal bones which are more stable but allow less movement.
Step-by-step explanation:
The range of motion of a movable joint is expressed in degrees. This is because the movement of joints involves the concepts of angular motion such as flexion, extension, and rotation, which are best described in terms of angles. In anatomy, the range of motion refers to the full movement potential of a joint, usually its range of flexion and extension. For instance, when discussing the shoulder joint, which allows a high degree of mobility, we consider how far the arm can move in different directions a measurement that is quantified in degrees. Diarthrosis, or freely mobile joints such as the synovial joints, have a wide range of movements which can be separated into categories like uniaxial, biaxial, or multiaxial, indicating the number of planes in which the joint can move.
The stability of a joint is inversely related to its mobility, meaning that the more mobile a joint is, the weaker it tends to be. This is due to the increased range of motion allowing more freedom of movement but simultaneously providing less support or structural rigidity. For example, the shoulder joint has a wide range of motion but is less stable compared to the carpal bones in the wrist, which are more stable but allow less range of motion.