Olkapäänivel

Olkapäänivel, also known as the glenohumeral joint, is the main articulation of the shoulder. It is a ball-and-socket joint formed by the head of the humerus (upper arm bone) fitting into the glenoid cavity of the scapula (shoulder blade). This specific structure allows for a wide range of motion, making the shoulder the most mobile joint in the human body. The extensive mobility, however, comes at the cost of inherent instability, which is managed by a complex system of muscles, ligaments, and tendons.

The glenoid cavity is relatively shallow compared to the humeral head, which contributes to the joint's flexibility. To enhance stability, the glenoid cavity is rimmed by the glenoid labrum, a fibrocartilaginous ring that deepens the socket and provides attachment points for ligaments. Surrounding the joint capsule are the rotator cuff muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles not only move the arm but also play a crucial role in stabilizing the humeral head within the glenoid cavity during movement.

The extensive range of motion of the olkapäänivel includes flexion, extension, abduction, adduction, internal rotation, external rotation, and circumduction. This versatility is essential for numerous daily activities, from reaching for objects to complex athletic maneuvers. Despite its stability mechanisms, the shoulder is susceptible to injuries such as dislocations, rotator cuff tears, and impingement syndrome due to its anatomical design and frequent use.