Posted on 01 Jun 2012 13:37
The teres major muscle is a small, round muscle lying along the lateral border of the scapula. It forms the inferior border of both the triangular space and quadrangular space. The muscle gets its name from its shape and size. Teres means "round" in Latin, and the term major refers to it being the larger of two muscles, the teres minor muscle lying just superior to the major. Both the teres major and minor are similar in shape, only the major is larger. It can be palpated in the trough between the lateral scapula and the latissumus dorsi, but is deeper than the lattisumus.
The teres major shares the same functions as the latissimus dorsi in internally rotating, adducting, and extending the shoulder, especially from the flexed position1. The teres major acts more strongly when the rhomboids and levator scapulae fix the inferior angle of the scapula2,4 or otherwise the scapula would move forward toward the arm. It is sometimes called the lat's little helper.
Both the teres major and the latissimus dorsi wrap around from the back of the armpit, with the latissimus twisting around the teres major to help form the axilliary fold, both attaching to the front of the upper humerus. The borders of the two muscles are joined for a short distance near the humeral attachments. They do not share the same attachments below, however. The teres major attaches to the scapula and the latissumus attaches to the wall of the chest.3 Together, the two form the thick posterior wall of the armpit.
Teres Major Muscle
Teres Major Origin, Insertion, and Action
Origin: Dorsal (posterior) surface of the lateral border of the scapula, just above the inferior angle below the teres minor.
Insertion: Medial lip of the intertubercular groove of the humerus just below the insterion of the subscapularis.
Action: Internal rotation, adduction, and extension of glenohumeral joint. More active during resisted adduction and extension of the arm from the flexed position to the posteriorly extended position. Weak adduction of the arm when acting alone but strongly adducts arm when the scapula is fixed the rhombodei and levatar scapulae. Also active during the backward swing of the arm when walking. Assists the latissimus dorsi in the wood chopping movement. Activated when writing or typing on a keyboard.2,4
Teres Major Trigger Points Causes and Symptoms
image by robswatski via flickr
Trigger Points in the teres major cause a deep ache in the posterior deltoid and over the long head of the triceps brachii muscle. Sometimes, pain is also referred to the posterior shoulder joint itself and to the dorsal forearm, but rarely the elbow. Trigger points in this muscle can cause sharp deltoid pain when resting your elbows on a table or desk or when reaching up and forward. Along with TrP's in the latissimus, reaching up and forward may be restricted with pain but the shoulder is not frozen.
Any activities that cause strain or overuse of the latissimus dorsi may also aggravate the teres major, such as pulling the arm downward (pullups, lat pulldowns), and tennis, rowing, swimming, wood chopping, and pitching. Travell and Simons mentions that one major known cause of trigger points in the teres major is the strain from driving a vehicle with faulty steering or no power steering, particululary large, heavy vehicles such as trucks that are difficult to steer.2,5
The symptoms of teres major trigger points may be confused with subacromial or subdeltoid bursitis, supraspinatus tendinitis, c6 to 67 radiculopathy or a thoracic outlet syndrome. The teres major is one of four muscles (pectoralis major, latissimus dorsi, and subscapularis) that are responsible for a pseudothoracic outlet syndrome that is actually of myofascial origin. However, it should be noted that trigger points in the scalenes, pectoralis minor, and subclavius muscles can produce a true thoracic outlet syndrome, which is caused by entrapment and compression of the brachial plexus and subclavian artery.3
Teres Major Trigger Points and Referred Pain Patterns
Teres Major Trigger Point Self-Treatment
There are two main areas of trigger points in the teres major muscle. One of the trigger points is more medial and overlaps the surface of the scapula. The other is more to the side. Both TrP's refer pain to the same locations as described above. There is a common trigger point area of the latissumus dorsi near the lateral teres major TrP, evidenced by pain of the mid-back along the lower inner edge of the scapula. Any self-treatment of the area may encounter both of these trigger points and it can be difficult, in self-treatment, to differentiate the teres major from the latissimus.
You can attempt to massage the muscle with your hand. Reach underneath your arm to grasp and pinch the wad of muscle under the armpit. Feel for any hyper-sensitive areas and massage, taking care to check the area just over the lower lateral border of the scapula, where the teres major attaches. The hand may be tired very quickly by this effort, however.
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This page created 01 Jun 2012 13:37
Last updated 23 Feb 2015 19:36