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Causes of Shoulder Pain
      The shoulder joint is unique among the body's joints in that it relies heavily upon the muscle groups in the region to actually hold the joint together. This lack of major bone and ligament support allows for the greatest freedom of arm movement. But it also requires the muscles to function properly for the joint to work effectively and stay healthy. As such, perhaps no joint in the body is affected as much by trigger points as the shoulder (glenohumeral) joint.
       Of all the muscle groups that act on the shoulder joint, the rotator cuff muscles are the most important. The rotator cuff muscle group is composed of the following muscles:
  • The Infraspinatus
  • The Supraspinatus
  • The Subscapularis
  • The Teres Minor
     These are small muscles that are easily overloaded by sporting and repetitive activities. Trigger points can cause chronic tension in these muscles, making them more likely to suffer tears.
     Trigger points in any of the muscles that attach to the shoulder blade can also play a significant role in shoulder dysfunction disorders. It is very important to address these trigger points, as they distort the proper movement of the shoulder blade during movements of the arm.

The Muscles and Trigger Points that Cause Shoulder Pain
      Shoulder pain is a complex disorder that can involve more than ten muscle groups. Clinical experience has shown that the following three muscle groups are involved most often:
  • The Infraspinatus
  • The Subscapularis
  • The Trapezius
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     The Infraspinatus muscle is found on the back of the shoulder blade and is one of the Rotator Cuff muscles. It attaches to the lower part of the shoulder blade and runs laterally to attach to the top of the upper arm bone (the humerus). Contraction of this muscle rotates the arm in the shoulder joint and stabilizes the shoulder joint during other movements.
      Trigger points in this muscle produce pain in the shoulder joint that radiates down the front and side of the arm. People with active Infraspinatus trigger points are unable to reach behind their back, and have difficulty combing their hair or brushing their teeth.
     Learn more about the Infraspinatus trigger points with this article from Dr. Perry > The Infraspinatus Trigger Points: Magicians of Shoulder Pain
     The Subscapularis muscle is one of the Rotator Cuff muscles. It lies deep in the armpit region and attaches to the inner surface of the shoulder blade. Like the other Rotator Cuff muscles, the Subscapularis contracts to rotate the arm, and to stabilize (hold together) the shoulder joint during movement of the arm.
      Trigger points in this muscle refer pain to the back of the shoulder, and also in a strap-like pattern around the wrist. These trigger points will also cause "frozen shoulder" syndrome, and will prevent a person from reaching their arm across to the other armpit.
       Learn more about the Subscapularis trigger points with this article from Dr. Perry > Subscapularis Trigger Points: The Icicles of Shoulder Pain.
     The Trapezius is the large, diamond shaped muscle group that forms the base of the neck and upper back region. It has attachment points at the base of the skull, along the spine, on the shoulder blade, and on the collar bone. When this muscle contracts it typically moves the shoulder blade, but it also plays a part in moving the neck and head.
     Trigger points in this muscle refer pain to the back and side of the neck, to the temple region, behind the ear or back of the head, and to the shoulder joint. Trigger points in this muscle develop for a number of reasons, including poor posture, emotional stress, whiplash injuries, falls, and sleeping positions (or sleeping under a ceiling fan). Trigger points in this muscle affect its ability to move the shoulder blade, and therefore will often contribute to common shoulder problems.
     Learn more about the Trapezius trigger points with these articles from Dr. Perry > The Lower Trapezius Trigger Point: A.K.A. the "Bitchy" Point and Trapezius Trigger Points Are Like Opinions...Everybody Has One.
Important: The following content is provided for information purposes only. A proper diagnosis of any condition requires a physical examination by a licensed doctor.
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