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The acromion forms the summit of the shoulder and is a large, somewhat triangular or oblong process, flattened from behind forward. It projects laterally at first, then curves forward and upward to overhang the glenoid fossa. [2] It starts from the base of acromion which marks its projecting point emerging from the spine of scapula. [3]
While this muscle prevents dislocation in the joint, strong forces tend to break the clavicle instead. The acromioclavicular joint, the joint between the acromion process on the scapula and the clavicle, is similarly strengthened by strong ligaments, especially the coracoclavicular ligament which prevents excessive lateral and medial movements ...
The coracoacromial ligament originates from the summit of the acromion of the scapula, just in front of the articular surface for the clavicle. [1] It inserts by its broad base along the whole length of the lateral border of the coracoid process of the scapula. [1] The clavicle and under surface of the deltoid muscle are above it.
The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius. [18] These two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop.
It is attached, by its apex, to the summit of the acromion just in front of the articular surface for the clavicle; and by its broad base to the whole length of the lateral border of the coracoid process. [2] This ligament, together with the coracoid process and the acromion, forms a vault for the protection of the head of the humerus.
The shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) (see diagram). Two joints facilitate shoulder movement. The acromioclavicular (AC) joint is located between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle.
A separated shoulder, also known as acromioclavicular joint injury, is a common injury to the acromioclavicular joint. [2] The AC joint is located at the outer end of the clavicle where it attaches to the acromion of the scapula. [2]
Animation of shoulder joint showing the supraspinatus muscle. The rotator cuff muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid cavity. The glenoid cavity is shallow and contains the glenoid labrum which deepens it and aids stability. With 120 degrees of unassisted flexion, the ...