movements

Last reviewed 01/2018

Movements between the acromion and clavicle at the acromioclavicular joint are indirectly the action of muscles acting upon the scapula. There is no direct muscular connection between the two bones. All acromioclavicular movements except axial rotation are associated with reciprocal movements at the sternoclavicular joints.

There are three degrees of freedom of movement at the acromioclavicular joint:

• protraction/retraction:
• axis passes through a point midway between the acromioclavicular joint and the lateral end of the clavicle
• retraction of scapula (acromion) is limited by the anterior part of the joint capsule and the trapezoid part of the coracoclavicular ligament
• protraction is limited by the posterior joint capsule and conoid ligament
• elevation/depression:
• elevation is limited by tension in the coracoclavicular ligaments
• depression is limited by impinging upon the inferior surface of the clavicle
• axial movement:
• the scapula may rotate medially or laterally about an axis of rotation through the conoid ligament and acromioclavicular joint
• for example, in elevation of the arm the scapula may rotate at the acromioclavicular joint for the first 20-25 degrees; then, the coracoclavicular ligaments are placed under tension. The rest of the rotatory movement of the scapula is permitted by rotation of the clavicle at the sternoclavicular joint.