Olkanivelestä

Olkanivelestä, or the shoulder joint, is a complex ball-and-socket joint that connects the upper arm bone (humerus) to the shoulder blade (scapula). It is the most mobile joint in the human body, allowing for a wide range of motion in various directions, including flexion, extension, abduction, adduction, rotation, and circumduction. This extensive mobility, however, comes at the cost of inherent instability, making it susceptible to injuries.

The shoulder joint is composed of three main bones: the humerus, the scapula, and the clavicle (collarbone). The articulation between the humerus and the scapula forms the glenohumeral joint, which is the primary component of the shoulder. The head of the humerus, a rounded prominence, fits into a shallow socket on the scapula called the glenoid cavity. This shallow socket provides less stability compared to the deeper sockets of other joints.

Supporting the glenohumeral joint are several structures, including the rotator cuff muscles and their tendons. These muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—surround the joint and play a crucial role in stabilizing the humerus and enabling its movement. Ligaments also reinforce the joint capsule, providing additional stability. The presence of the acromioclavicular joint, where the clavicle meets the acromion (a part of the scapula), also contributes to the overall shoulder complex. Injuries to any of these components, such as rotator cuff tears, dislocations, or impingement syndrome, can significantly impair shoulder function and cause pain.