CHAPTER 15: Shoulder Joint and The Arm

Home | OG anatomy | Gross Anatomy | Topic index | Chapter 15

The Acromioclavicular Joint
 
Classification  
The acromioclavicular joint is a synovial joint of the plane or gliding type .
Articulating Surfaces  

Both of the articular surfaces involved are flat and oval.
The facet on the acromial end of the clavicle faces downwards and laterally
The facet on the medial edge of the acromion faces upwards and medially

 
Capsule  
The fibrous capsule unites the articular margins. It is thickened above to form the acromioclavicular ligament, which resists the tendency for the clavicle to glide laterally. An intra-articular disc is usually present.
Synovial membrane  
Lines the capsule and both sides of the disc.
Relations  
Superior  

The joint is subcutaneous above. Fibres of the deltoid and of trapezius are attached to the capsule. The deltoid extends on to the anterior surface and trapezius on to the posterior surface.

Anterior  

The coraco-acromial ligament is attached just in front of the scapula.

Inferior  

The subacromial busa separates it from supraspinatus.

Blood-supply And Innervation

Blood Supply

Derived from branches of the suprascapular and thoraco-acromial arteries.

Innervation

suprascapular nerve

Movements  

Forward and backward gliding movements can occur and the scapula can rotate in its own plane.
These movements are important as part of the total mechanism of the pectoral girdle, when the scapula swings on the coracoclavicular ligament and the clavicle moves at the sternoclavicualr joint.