What is the Rotator Cuff?

The rotator cuff is a group of 4 muscles in your shoulder. 

Imagine keeping a golf ball on a tee. The rotator cuff muscles surround the shoulder joint, keeping the head of your upper arm bone firmly within the shallow socket of the shoulder.

A rotator cuff injury can cause a dull ache in the shoulder, which often worsens when you raise your arm overhead or sleep on the involved side.