Rotator cuff
From Free net encyclopedia
Image:Gray412.png The rotator cuff is an anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder.
These muscles arise from the scapula and connect to the head of the humerus forming a cuff at shoulder joint. They are important because they hold the head of the humerus in the small and shallow glenoid fossa of the scapula. The glenohumeral joint is often likened to a golf ball sitting on a golf tee. During elevation of the arm, the rotator cuff compresses the glenohumeral joint 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 and the efficiency of the deltoid muscle would be much less.
The four muscles that compose this group are:
- Supraspinatus muscle, which comes from the supraspinous fossa of the scapula. This abducts the arm.
- Infraspinatus muscle, which comes from the infraspinous fossa of the scapula. This laterally rotates the arm.
- Teres minor muscle, comes from the lateral border of the scapula, and also laterally rotates the arm.
- Subscapularis muscle, originating from the subscapular fossa of the scapula. This muscle medially rotates the humerus.
This group of tendons can become torn, leading to pain and restricted movement of the arm. A torn rotator cuff can occur following a trauma to the shoulder or it can occur through "wear and tear" of the tendons under the acromion. It is an injury frequently sustained by athletes whose duties involve making repetitive throws, such as pitchers in baseball. It is commonly associated with motions that require repeated overhead motions or forceful pulling motions.
A mnemonic to remember what muscles form the rotator cuff is SITS (supraspinatus, infraspinatus, teres minor, subscapularis) - someone with a rotator cuff injury sits out.
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