Final answer:
The shoulder joint, or glenohumeral joint, has a large range of motion but is not considered extremely stable due to its structural design, which favors mobility over stability.
Step-by-step explanation:
The shoulder joint, also known as the glenohumeral joint, is a ball-and-socket joint that offers a wide range of motion. It is formed by the articulation between the head of the humerus and the glenoid cavity of the scapula. While this joint allows for the largest range of motion of any joint in the body, it is not extremely stable due to its loose articular capsule and lack of structural support. The increased mobility comes at the expense of stability, making the shoulder more susceptible to dislocation and injury compared to more stable joints like the carpal bones in the wrist.
The glenohumeral joint enables flexion/extension, abduction/adduction, circumduction, and medial/lateral rotation of the humerus. Despite some support from intrinsic ligaments such as the coracohumeral ligament and the glenohumeral ligaments, the primary support for the shoulder joint comes from the muscles crossing the joint whose tendons form the rotator cuff. Additionally, the subacromial bursa and subscapular bursa help protect these muscle tendons from friction against the scapula.