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THE SHOULDER

The shoulder is a highly mobile ball-and-socket joint that connects the upper arm to the torso. It is formed where the head of the humerus (upper arm bone) fits into the shallow socket of the scapula called the glenoid cavity. This joint allows a wide range of movements including flexion, extension, abduction, adduction, rotation, and circumduction. The shoulder’s stability relies on muscles, tendons, and ligaments, especially the rotator cuff muscles, which surround the joint and help keep the humeral head securely in place. The clavicle (collarbone) and scapula (shoulder blade) also play key roles in shoulder movement and positioning. Due to its complex structure, the shoulder balances mobility with stability, making it essential for various arm and upper body functions.

The shoulder joint, known as the glenohumeral joint, is a ball-and-socket joint formed by the articulation of the head of the humerus and the glenoid cavity of the scapula. This shallow socket allows for a wide range of motion but relies heavily on surrounding muscles and ligaments for stability. The shoulder complex also includes the clavicle (collarbone) and scapula (shoulder blade), which work together to support arm movement and provide attachment points for muscles. The acromioclavicular and sternoclavicular joints connect the clavicle to the scapula and sternum, respectively, allowing additional mobility. The bones of the shoulder are covered with articular cartilage to facilitate smooth movement, while the joint is enclosed in a fibrous capsule lined with synovial membrane to reduce friction. This bony and joint structure provides the shoulder with exceptional mobility essential for lifting, reaching, and rotating the arm.
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