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What causes shoulder pain?

Rick Olderman
Physical Therapy Specialist

Assuming you've ruled out heart, cancer, or other non-musculoskeletal issues, shoulder pain can be caused by a few different mechanical problems.

It's important to understand that the shoulder blade houses the socket of the shoulder joint and the arm bone provides the ball to form this ball and socket joint. The shoulder blade is the platform from which the arm bone moves and so it's important to check its movement in terms range of motion, timing, resting, and moving landmarks. 

There are three sets of muscles controlling the arm and shoulder blade. These are:

  1. scapulohumeral muscles-which run from the shoulder blade to the arm bone;
  2. scapulothoracic muscles-running from the trunk to the shoulder blade; and,
  3. thoracohumeral muscles-connecting the trunk to the arm bone.

That's a lot of muscles, the reason being the shoulder is a floating system, completely controlled by those muscles (unlike, say, a knee joint which uses compression to help guide movement).

Another reason shoulder pan happens is due to the shape of the trunk. If you have a rounded or a flat trunk, this changes how the shoulder blade rests and moves.

Lastly, we can't forget movement patterns. It could be that you're not using the arm and shoulder correctly. This comes about through faulty exercise or work habits or a combination of all the elements we've discussed.

Shoulder pain often originates in the rotator cuff, the group of muscles and tendons that cover the shoulder joint. These tendons are already vulnerable to injury from normal activities. Injuries can also be caused by trauma or athletic activities.

In severe cases, partial or complete tendon tears can cause pain and weakness in the joint.

A dislocated shoulder is both painful and disconcerting, as people may be bothered by the sense of instability, as the ball of the shoulder slips out of the socket. Pain intensifies if the cartilage ring (labrum) around the socket tears.

Occasionally, ligaments may tighten, causing decreased range of motion. People may be unaware this is happening until they’re unable to raise their arm and their shoulder becomes frozen and painful. This is more common in people with diabetes or other endocrine disorders.

Arthritis can also cause shoulder pain. As the smooth surfaces of the ball and socket wear out, the cartilage becomes rough or may be absent altogether. The resulting pain can be disabling

Pinpointing the precise source of shoulder pain is important. Pain may be from a shoulder problem or stem from another issue, such as nerve irritation in the neck. This is called referred pain.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.