acromioclaviculares

The acromioclavicular joints, or AC joints, are the joints between the lateral end of the clavicle and the acromion process of the scapula on each shoulder. Each AC joint is a planar synovial joint with a thin capsule. The capsule is reinforced by the acromioclavicular ligaments, including the superior and inferior bands, and by the coracoclavicular ligaments (the conoid and trapezoid), which extend from the coracoid process to the clavicle and help suspend the upper limb.

Functionally, the AC joint allows small gliding movements that contribute to scapular rotation during arm elevation and overhead activities. Its stability depends on the integrity of the acromioclavicular and coracoclavicular ligaments, as well as surrounding muscles and fascia.

Injury and disease commonly involve the joint. An acute fall onto the shoulder can cause an AC joint sprain or shoulder separation, with injuries classified by the Rockwood system (types I–VI) describing varying degrees of ligament disruption and clavicular displacement. Most type I–II injuries are managed nonoperatively with rest, immobilization, and rehabilitation; higher-grade injuries (types III–VI) may require surgical reconstruction or fixation, especially in athletes, manual laborers, or when there is persistent instability or pain.

Radiology and diagnosis rely on clinical examination and radiographs, often with bilateral comparisons and specialized views to assess displacement. MRI or CT may be used to evaluate associated injuries or to guide surgical planning.

Other conditions affecting the AC joints include degenerative osteoarthritis and chronic pain syndromes, particularly in individuals engaged in heavy lifting or overhead sports. Management ranges from conservative care to surgical options such as distal clavicle excision or reconstruction of the coracoclavicular ligaments.