PT Classroom - Infraspinatus Trigger Points - A Contributor to Shoulder Pain  ׀ by Chai Rasavong, MPT, COMT, MBA

Shoulder pain is a common clinical problem seen by physical therapists. The cause of shoulder pain can be contributed to a variety of issues from structural to biomechanical. Often times injury to the rotator cuff can contribute to shoulder pain. The rotator cuff is comprised of a group of four muscles in the shoulder: supraspinatus, infraspinatus, subscapularis and teres minor. Most often in the therapy realm when one mentions a rotator cuff injury, the first thought would be to associate an injury to the supraspinatus muscle. However, other issues can occur at the other muscles comprising the rotator cuff as well. For this article we will examine trigger points at the infraspinatus muscle and its pain referral pattern.

The infraspinatus muscle originates at the medial three quarters of the infraspinous fossa of the scapula and fibrous intermuscular septa. It inserts at the middle facet of the greater tuberosity of the humerus and capsule of the shoulder joint. Its action is to laterally/externally rotate the arm and stabilize the shoulder joint. A study by Bron et al found that trigger points were most prevalent at the infraspinatus muscle compared to other muscles in the shoulder/girdle region and could be the underlying mechanism to shoulder pain (1). Simons & Travell describes trigger points as “a discrete, focal, hyperirritable spots located in a taut band of skeletal muscle. The spots are painful on compression and can produce referred pain, referred tenderness, motor dysfunction, and autonomic phenomena (2)". The trigger points at the infraspinatus muscle can project to the front of the shoulder (intra-articular pain) and the mid deltoid region, extending downwards to the arm to the ventrolateral aspect of the arm and forearm and the radial aspect of the hand (3). The referred pain from the muscle can mimic the symptoms of carpal tunnel syndrome (3)

In the physical therapy realm a multitude of techniques and tools can be utilized to address trigger points. These include dry needling, osteopathic manual techniques, soft tissue mobilization, myofascial release, acupressure, ultrasound, application of heat or ice and electrical nerve stimulation. A study by Hsieh et al found that dry needling was effective with inactivation of trigger points (4). Another study by Bron et al found that treating trigger points with manual therapy techniques and cold application was effective in reducing symptoms, reducing the number of muscles with active MTrPs and improving shoulder function in patients with chronic shoulder pain (5) .

There are a variety of studies which addresses treating trigger points but more research is warranted with larger sample sizes and more controlled studies. Nevertheless, hopefully this article will stimulate further insight at looking at trigger points at the infraspinatus as a possible contributor to shoulder pain.

Last revised: June 24, 2016
by Chai Rasavong, MPT, COMT, MBA

References
1) Bron C, et al. High prevalence of shoulder girdle muscles with myofascial trigger points in patients with shoulder pain. BMC Musculoskelet Disord. 2011 Jun 28;12:139. doi: 10.1186/1471-2474-12-139.
2) Simons DG, Travell JG, Simons LS. Travell & Simons' Myofascial pain and dysfunction: the trigger point manual. 2d ed. Baltimore: Williams & Wilkins, 1999:5.
3) Dommerholt J, Fernandez-de-las-Penas C. Trigger Point Dry Needling: An Evidenced and Clinical Based Approach. China: Churchill Livingstone Elsevier, 2013:96.
4) Hsieh YL, et al. Dry needling to a key myofascial trigger point may reduce the irritability of satellite MTrPs. Am J Phys Med Rehabil. 2007 May;86(5):397-403.
5) Bron C, et al. Treatment of myofascial trigger points in patients with chronic shoulder pain: a randomized, controlled trial. Am J Phys Med Rehabil. 2007 May;86(5):397-403.