Upper Limb

Acromioclavicular Joint (ACJ)

Reading Time:

Overview


The joints of the upper limb move in a coordinated and synchronous pattern. The acromioclavicular joint is a gliding synovial joint formed between the acromion of the scapula and the lateral articulating surface of the clavicle. The joint is supported by numerous ligaments and is easily palpated under the skin.

Gross Anatomy


The acromioclavicular joint is a gliding synovial joint, and is formed between the acromion of the scapula (a hook like superior process on the scapula), and the clavicle (an s shaped bone, also known as the collar bone). There is frequently a fibrocartilaginous disc interposed between the two bones. 


 

The joint is stabilised by the acromioclavicular ligament, which is comprised of superior, inferior, anterior and posterior components. The superior part of the ligament confers the most stability to the joint. The coracoclavicular ligaments, the conoid and trapezoid, arise from the conoid tubercle and trapezoid line on the lateral part of the inferior surface of the clavicle and insert onto the coracoid process of the scapular, and provide vertical stability to the joint. The joint capsule merges with the fibers of the trapezius muscle, with the deltoid muscles covering the joint superficially. All three structures provide additional stability to the joint. The subacromial bursa is a large bursa that sits under the acromial arch. It can become infected or inflamed, and may require antibiotics, drainage or removal.


The majority of movement that occurs involving the joint, is actually movement of the clavicle or scapula. The joint allows for a large amount of clavicular rotation (40-50 degrees), with the remainder provided by scapular rotation. Movements that occur at the joint are gliding during scapular protraction and retraction, tilting of the acromion and clavicle and rotation during abduction and adduction of the shoulder.

Clinical Anatomy


Lorem ipsum dolor sit amet, sapien platea morbi dolor lacus nunc, nunc ullamcorper. Felis aliquet egestas vitae, nibh ante quis quis dolor sed mauris.

Quick Anatomy


Key Facts

Developmental precursor: Limb bud, somatic layer of lateral mesoderm 
Blood supply: Thoraco-acromial and suprascapular arteries 
Nerve supply: Axillary, suprascapular and lateral pectoral nerves 
Bursae: Subacromial bursa

Aide-Memoire

Most professional rugby players have injured this joint in some capacity!

Summary


The acromioclavicular joint is a gliding synovial joint formed between the acromion of the scapula and the flat lateral articulating surface of the clavicle. The joint is supported by numerous ligaments, but lies relatively superficially, under the skin and is easily palpated.

References


Lorem ipsum dolor sit amet, sapien platea morbi dolor lacus nunc, nunc ullamcorper. Felis aliquet egestas vitae, nibh ante quis quis dolor sed mauris.