What Is My Rotator Cuff, and Why Does It Hurt?

What Is a Rotator Cuff?

Your rotator cuff is made up of muscles and tendons that keep the ball (head) of your upper arm bone (humerus) in your shoulder socket. It also helps you raise and rotate your arm. It’s a complicated process that your body makes look easy.

Rotator cuff muscles

Each one of the following muscles is part of the rotator cuff and plays an important role:

• Supraspinatus. This holds your humerus in place, keeps your upper arm stable, and helps lift your arm.
• Infraspinatus. This is the main muscle that lets you rotate and extend your shoulder.
• Teres minor. This is the smallest rotator cuff muscle. Its main job is to help with rotation of your arm away from your body.
• Subscapularis. This holds your upper arm bone to your shoulder blade and helps you rotate your arm, hold it straight out, and lower it.

These muscles are attached to your arm bone with tendons that form a covering (cuff) over the ball of the humerus.

Your rotator cuff helps you do things like get something off a high shelf and comb your hair. It’s especially important in sports like baseball, swimming, and tennis.

Rotator Cuff Injuries

• Rotator cuff tear. The tendons in your shoulder can become frayed, partially torn, or completely detached from the bone. It's often the result of wear and tear from daily use over time. You’re more likely to have this if you have a job where you need to move your arm a certain way over and over, like a painter or a carpenter, or you play sports like tennis and baseball. It also can happen suddenly if you fall on your arm or try to lift something heavy.
• Rotator cuff tendinopathy. Formerly called tendinitis, this is inflammation or irritation of a tendon that attaches to a bone. It causes pain in the area just outside the joint. Common types of tendinopathy include pitcher’s and swimmer’s shoulder.
• Bursitis. The bursa (a small sac filled with fluid that protects your rotator cuff) can get irritated when you repeat the same motion over and over again, like throwing a baseball or lifting something over your head. Bursitis also can be caused by an infection.