Articular capsule of acromioclavicular joint
Capsula articularis articulationis acromioclavicularis
The thin fibrous capsule surrounding the small plane joint between the lateral end of the clavicle and the acromion of the scapula.
At a glance
- English
- Articular capsule of acromioclavicular joint
- Latin (TA2)
- Capsula articularis articulationis acromioclavicularis
- System
- Joint
- Region
- Upper limb
- Side
- Paired, left and right
About the articular capsule of acromioclavicular joint
The acromioclavicular joint lies at the top of the shoulder, where the flat lateral end of the clavicle meets a small facet on the medial edge of the acromion. It is a plane synovial joint, and the bony ends are covered by fibrocartilage rather than ordinary hyaline cartilage. A wedge-shaped articular disc often hangs into the joint from above, though it is frequently incomplete.
The capsule is a loose fibrous sleeve attached around the margins of the two facets and lined by synovial membrane. It is weak on its own. Above, it is thickened by the superior acromioclavicular ligament, which is strengthened further by fibres of the trapezius and deltoid that blend with it. Below, a thinner inferior acromioclavicular ligament completes it. The strength that actually holds the clavicle down on the acromion comes from outside the capsule, from the conoid and trapezoid parts of the coracoclavicular ligament.
The joint lets the scapula glide and rotate on the end of the clavicle as the arm is raised. A fall onto the point of the shoulder is the usual cause of a separation. In mild injuries only the capsule and its ligaments are sprained; in more severe ones the coracoclavicular ligament also tears and the end of the clavicle rides up, giving a visible step at the shoulder. The joint is also a common site of osteoarthritis, causing pain at the top of the shoulder when the arm is lifted above the head or brought across the body.
Attachments and function
- Formed by
- Margins of the acromial facet on the lateral end of the clavicle.
- Joins
- Margins of the clavicular facet on the medial border of the acromion.
- Movements
- Encloses the joint and gives it limited stability, allowing the scapula to glide and rotate on the clavicle during arm movements.
- Nerve supply
- Suprascapular and lateral pectoral nerves.
- Blood supply
- Acromial branch of the thoraco-acromial artery and branches of the suprascapular artery.
Anthromica
See the articular capsule of acromioclavicular joint where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
