clavicleacromion

Clavicleacromion, though not a standard anatomical term, commonly refers to the acromioclavicular joint, the articulation between the clavicle and the acromion of the scapula. It is located at the top of the shoulder, where the lateral end of the clavicle meets the acromion process, forming part of the shoulder girdle.

Anatomy and ligaments: The acromioclavicular joint is a synovial diarthrosis with primarily plane (gliding) movement. Its articular surfaces are the inferior aspect of the acromion and the lateral end of the clavicle, typically covered by hyaline cartilage. The joint capsule surrounds the articulation and is reinforced by ligaments, including the acromioclavicular ligament (formed by superior and sometimes inferior components) and the coracoclavicular ligaments, which consist of the conoid and trapezoid. The coracoclavicular ligaments suspend the clavicle from the coracoid process and provide major vertical stabilization. The coracoacromial ligament forms part of the coracoacromial arch but is not a primary stabilizer of the AC joint.

Function: The joint permits small gliding and rotational movements that accompany shoulder motion, particularly during arm elevation. It works with scapulothoracic motion to enable the full range of shoulder movement, contributing to the scapulohumeral rhythm that increases the arm’s abduction and flexion.

Clinical significance: The acromioclavicular joint is a common site of sports-related injury, often termed an AC joint separation. Injuries range from ligament sprains (commonly Type I–III) to more severe dislocations (Types IV–VI) in various classification schemes. Diagnosis uses clinical examination and radiographs, with advanced imaging as needed for complex injuries. Degenerative changes can produce pain and stiffness in older individuals.