How Does the Rotator Cuff Stabilize the Shoulder?

Written by Ensley Alden, Beth’s 12’s SoCal

(With help from Gwen Alden, PT/Owner HealthWest Therapy)

The shoulder is made up of many parts. Muscles and nerves work together to help it move. There are four muscles that make up the rotator cuff: the Subscapularis, the Supraspinatus, the Infraspinatus, and the Teres Minor. These four muscles help perform daily activities.


The four important muscles in the rotator cuff work together to move the arm in many different directions, hence it’s name. Each muscle of the rotator cuff meet at the scapula, then connected with the humerus.

The Subscapularis, along with the upper and lower subscapular nerves connect from one side of the scapula to stabilize the humerus in the glenoid cavity. The Supraspinatus lies on the upper part of the scapula and attaches to the greater tubercle of the humerus. The Infraspinatus inserts in the middle of the humerus and allows the arm to move laterally. Finally, the Teres Minor borders the scapula which then connects to the lowest point on the humerus.

All four rotator cuff muscles play a role in when and how the arm moves. Together they stabilize the upper arm bone, the GH joint (Shoulder), and provide the wide range of motion the shoulder should be able to move.


The shoulder or rotator cuff is a common area to have injuries, especially if you play sports like volleyball, frequently pitch a baseball, or swing a tennis racket. This constant movement can make cartilage wear down and result in replacement of what was needed to prevent friction. The most common injuries can be from a tear in any of the muscles that make up the shoulder, really. Although it a tear usually occurs in the rotator cuff, it can also happen on the outer layer of muscle that protects the rotator cuff.

Various jobs that require reaching overhead for an extended amount of time can damage the shoulder with the repeated motion. These jobs can be similar to being a carpenter or painter.

More common injuries include RT tendonitis, RT Tendonosis, and impingement. Tendonitis usually occurs in athletes like Volleyball players, Soft/Baseball pitchers, and Swimmers. This is basically overusage of the shoulder. Tendonosis symptoms can come slowly and make one feel uncomfortable. This pain can go all the way down to your elbow. Simple things can hurt your shoulder like reaching for something that is in front of you or extending it to the side. Impingement occurs when a muscle in the RT swells and cramps up the space in between the arm and shoulder bones. If the upper arm starts to have cramps or little movements are shocking it, be honest to your doctor or physical therapist so you can seek help immediately. Not treating it in time may result in the injury becoming worse or never being able to work the same again.

 Falling on your side/shoulder can tear a tendon in the rotator cuff. Theses sort of injuries usually result in surgery, so don’t hesitate to talk to your doctor. Also, if a tendon in the rotator cuff is over extended or hyperextended too far, this can tear it.

Shoulder pain can mean different things at different ages. If the shoulder hurts at ages 15-30, it probably is in pain due to instability where the shoulder ligaments are loose. Older patients from the ages 30 and up suffer from degenerative problems in the shoulder.

Tears in tissue can gradually grow overtime. They start small, but to prevent further damage, rest, ice, and talk to your doctor. If there has been a tear for a while, it probably has turned into fat and is not capable to work like a muscle.

To find if you have an injury, a doctor will take an X-ray or MRI. Surgery can help if it’s absolutely needed. You should be honest about your injury.    

Physical Therapy exercises can improve flexibility and strength of the muscle surrounding the shoulder. Although the exercises can help restore strength, a major injury requires more attention.


Surgical treatment is required if your pain/symptoms have gone on for 6-12 months, if you have a 3+ cm tear, or if you have significant weakness in your shoulder. Some symptoms of RT conditions are pain, and weakness. To get rid or reduce the pain level of the injury, you can rest, ice, and use pain relievers. These are all effective treatments. Steroid injections  helps if no other treatment is available or your pain doesn’t go away.

 A form of surgery is called Arthroscopic surgery. It involves small[few] incisions and a camera. No matter what type of surgery is performed on the injury, it is still required to get physical therapy after.

Another effective treatment is PT where one can receive Ultrasound, E-stim, massage, advice, and exercises.

There are some exercises that you can do to help build back strength. You can do external rotation, high-low rows, the reverse fly, all helping strengthen what’s weak. An exercise you can do to stretch the shoulder is called the crossover arm. You bring the arm across to the opposite side and hold with the other arm. The Pendulum: let the arm hang freely while the other is on a higher surface like a table/counter. Swing your arm in a circular motion, repeat. The passive internal rotation: hold a stick in front of your body, keep elbows on body and move horizontally.

All of these stretches somehow helps to restore strength and help recover from major or small injuries.

The rotator cuff is an important muscle that helps your arm become stronger, or weaker. It is important to any movement made by the shoulder. It is a vital element to what makes us able to reach for what we do.