What Is It?
Four tendons attach muscles from the shoulder blade and ribs to the upper arm bone (humerus). Because these tendons help to rotate the arm within its socket, this sleeve of tendons is called the rotator cuff.
Tendons in the rotator cuff can be injured easily because they move within a tight space. When the shoulder is turned or lifted at the limit of its natural range of movement, the tendons in this tight space are moved, too. Occasionally, the rotator cuff tendons can bump or rub against a bony knob (the acromion) above them or against a ligament at the front of the shoulder.
This friction is known as impingement syndrome and causes inflammation in the rotator cuff. Rotator cuff friction is most likely to cause inflammation if your shoulder movement is rough or repetitive. Inflammation can cause three problems:
Several types of shoulder use commonly trigger rotator cuff injury:
In addition, your shoulder can be injured more easily if it is out of shape. The narrow space that envelops the rotator cuff tendons becomes even narrower if your shoulder muscles are weakened or tight. When this happens, routine shoulder movements are more likely to cause tendon friction.
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