Infraspinatus Muscle: Location, Action, and Trigger Points

Posted on 19 Nov 2016 19:26

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The infraspinatus muscle is a thick, triangular muscle which occupies most of the concave, dorsal surface of the scapula, a part of the scapula called the infraspinatus fossa. In other words, this muscle covers almost the entire scapula (shoulder blade) below the scapular spine.

The muscle gets its name from its location: Spinatus refers to the spine of the scapula and infra means below or beneath. Use the labeled image of the scapula below to locate its different parts.

Together with the subscapularis, supraspinatus, and teres minor, the infraspinatus helps make up the rotator cuff. This group of muscles, which contribute to external and internal rotation of the shoulder, have angles of pull that allow them to provide dynamic stabilization of the shoulder joint, assisting to stabilize the humeral head in the glenoid fossa. The rotator cuff, along with the deltoid muscle, makes up one of the most important force couples in the body. The muscle is innervated by the suprascapular nerve.

The infraspinatus is particularly sensitive to trauma and wear and tear from overuse, especially among tennis players, overhead throwing athletes, skiers, swimmers, and anyone who must use excessive overarm movements. Overuse of the infraspinatus leading to infraspinatus tendinitis will usually cause the muscle to be inhibited, which will greatly affect glenohumeral stability, which will lead to further deficiencies in shoulder function.

Infraspinatus Origin, Insertion, and Action

Origin: The infraspinatus, in most cases, has three pennate origins on the infraspinatus fossa just below the spine of the scapula.

Insertion: Posterior of greater tubercle of humerus.

Action: External rotation of the glenohumeral joint, together with teres minor; horizontal abduction of the glenohumeral joint, extension of the glenohumeral joint, stabilization of the humeral head in the glenoid fossa.


labelled infraspinatus muscle
labelled infraspinatus muscle


Infraspinatus Trigger Points Referred Pain and Symptoms and Causes

Due to its importance in shoulder movement, there are many common activities that can lead to trigger points in the infraspinatus and it is one of the most frequently injured or overloaded muscles in the body. This is especially true for overhead throwing athletes. In addition to sports activities, anything that requires your hands to be over your head for long periods, reaching back repeatedly, driving with hands on top of the wheel, typing on a computer without elbow support, etc. can cause overload to the muscle.

When trigger points of the infraspinatus occur, there may also be trigger points in the supraspinatus and perhaps the levator scapulae.

Infraspinatus trigger points occur on the upper part of the muscle, just under the scapular spine, which is the bony ridge at the top of the shoulder blade, easily palpated. Trigger points may also occur along inner scapular border.

The trigger points below the scapular spine refer pain to the front of the shoulder, felt as a deep ache in the joint. This pain may spread down the biceps muscle and even down the forearm and into the wrist and hand, affecting the entire thumb. Due to pain felt where the biceps attaches at the shoulder, this pain may be mistaken for biceps tendinitis. Pain may sometimes be felt in the back of the neck on the same side as the trigger points occur. Trigger points along the inner scapular border may refer pain between the shoulder blades on the same side. See the trigger point image below.

infraspinatus trigger points and referred pain patterns

Infraspinatus Trigger Points and Referred Pain Patterns

infraspinatus trigger points and referred pain patterns

Infraspinatus Trigger Points and Referred Pain Patterns

Reaching behind, such as to retrieve your wallet, fasten a bra, or zip a dress, can be very painful due to infraspinatus trigger points. Lying on the affected side at night can cause more pain, and sometimes lying on the back can be difficult.

Infraspinatus Trigger Point Treatment

Trigger points in the infraspinatus are easily massaged with a Thera Cane, Backnobber, or tennis ball against the wall. To use a tennis ball, follow a similar procedure as given for rhomboid trigger points. If you have symptoms, especially pain in the front of the shoulder, find the trigger points by pressing on the areas given here, until you feel a tenderness. You may not at first feel anything but it won't hurt to give your infraspinatus a massage and the tenderness may come later. Use gentle strokes a first and limit the treatment to five or six strokes, but repeat several times during the day.

If your pain symptoms do not subside, are too complicated, do not hessitate to consult a proffessional. For more information, you may want to buy the Trigger Point Therapy Workbook by Clair Davies.

This "Infraspinatus Muscle: Location, Action, and Trigger Points" page is provided by Ground Up Strength for information purposes only and should not take the place of professional medical advice. Although we have done our utmost to provide accurate and safe information, we are not medical professionals and the information on this page should not be taken as professional medical advice, or any other kind of medical advice. Any self-treatment undertaken by you is undertaken at your own risk.

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Unless otherwise noted, all images on this page used under license. Images by LifeART (and/or) MediClip image copyright 2010. Wolters Kluwer Health, Inc.- Lippincott Williams & Wilkins. All rights reserved. Images not for reuse..

Resources
1. Simons, David G., Janet G. Travell, Lois S. Simons, and Janet G. Travell. "Chp. 8: Masseter Muscle." Travell & Simons' Myofascial Pain and Dysfunction: the Trigger Point Manual. Baltimore: Williams & Wilkins, 1999. 329. Print.
2. Davies, Clair. The Trigger Point Therapy Workbook: Your Self-treatment Guide for Pain Relief. Oakland, CA: New Harbinger Publications, 2004. Print.
3. Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998.

This page created 19 Nov 2016 19:26
Last updated 19 Nov 2016 20:52

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