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The supraspinatus muscle performs abduction of the arm, and pulls the head of the humerus medially towards the glenoid cavity. [5] It independently prevents the head of the humerus from slipping inferiorly. [5] The supraspinatus works in cooperation with the deltoid muscle to perform abduction, including when the arm is in an adducted position. [5]
The rotator cuff compresses the glenohumeral joint during abduction of the arm, an action known as concavity compression, in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa, lessening the efficiency of the deltoid muscle.
Lateral rotation (in abduction: 95°; in adduction: 70°) Infraspinatus: Infraspinous fossa of scapula Greater tubercle of humerus Teres minor Upper two thirds of lateral border of scapula Greater tubercle of humerus Posterior fibers of deltoid Spine of scapula Middle of lateral surface of shaft of humerus Medial rotation (in abduction: 40 ...
External rotation (or extorsion or lateral rotation) is an anatomical term of motion referring to rotation away from the center of the body. The external rotator muscles include: Muscles
The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius. [10] 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.
Abduction is an anatomical term of motion referring to a movement which draws a limb out to the side, away from the median sagittal plane of the body. It is thus opposed to adduction . Upper limb
External rotation (lateral rotation or extorsion) is rotation away from the center of the body, [22] carried out by external rotators. Internal and external rotators make up the rotator cuff , a group of muscles that help to stabilize the shoulder joint .
Shoulder anatomy, front view Shoulder anatomy, back view. The rotator cuff is an anatomical term given to the group of four muscles and their tendons that act to stabilize the shoulder. [3] These muscles are the supraspinatus, infraspinatus, teres minor and subscapularis and that hold the head of the humerus in the glenoid cavity during ...