The teres minor is a muscle located in the rotator cuff that is part of the shoulder. Its primary purpose is to help rotate the shoulder joint externally and it does this in conjunction with the infraspinatus — another of the four rotator cuff muscles. Rotator cuff injuries can be caused either by sudden movements or through chronic tears which occur because of repeated strain.
The origin of the teres minor is on the dorsal exterior of the scapula. The fibers run laterally and in an upward direction before becoming a tendon. This tendon inserts at the humerus. The innervation of the muscle is via the axillary nerve. In some rare situations the teres minor may be partly joined to the infraspinatus.
The main action of the teres minor muscle is to rotate the shoulder externally. This happens through a lateral rotation of the humerus head. Aside from rotation, the muscle is also used to hold the humerus head in the correct position with regards to the scapula. The muscle also helps to adduct the arm along with other muscles.
There are two teres muscles — the major and minor. The teres major performs similar actions to the minor although it helps internal rotation and is only active when the scapula is fixed. Other rotator cuff muscles include the supraspinatus, infraspinatus and sucscapularis.
Rotator cuff injuries are relatively common and can be caused by a number of reasons. For example, any sports that involve repeated rotation of the shoulder may place more strain on the rotator cuff muscles. Acute tears happen when a sudden and powerful movement by the athlete causes a tearing of one of the muscles. This is usually immediately obvious as it can be a painful injury.
Chronic rotator cuff injuries occur over a much longer period of time and often affect the tendon more than the muscle itself. If the tendon starts to rub against the bone then this can cause inflammation. This is sometimes known as impingement syndrome and commonly affects people over the age of 40.
Treatment for a rotator cuff injury depends on the severity of the problem and how it was caused. If the injury was caused by a sudden movement then rest and ice will help to reduce the swelling. Chronic injuries follow similar treatment principles, although an injection may be required to control the inflammation and reduce pain. Surgery may be required for either type in some situations.