What Exactly IS the Rotator Cuff?
Rotor Cup, Rotary Cuff, Rotator Cup… we’ve heard them all. These are just some of the names people use to refer to the main structure of the shoulder. To clear things up, the correct term is “rotator cuff.” Often, when clients come in with a diagnosed rotator cuff injury, we ask them which muscle is affected. The usual response is a blank stare followed by, “Well…the rotator cuff…like I told you.” So, let’s break down the different parts of the rotator cuff and what they do.
The rotator cuff refers to a group of four muscles that cross the shoulder joint, providing various actions for the arm. These muscles are the supraspinatus, infraspinatus, subscapularis, and teres minor. Together, they form a cuff-like structure that holds the arm in place in the shoulder socket, each muscle stabilizing and moving the arm in different planes. They work as a team, and when one muscle is injured, the others are often affected too. Given the shoulder’s complexity, a rotator cuff injury can also involve other neck and upper back muscles, leading to neck pain and even headaches on the affected side.
The supraspinatus muscle sits at the top of the scapula (the “wing” in your upper back), right above the spine of the scapula. Its name comes from its placement: supra = above, spinatus = spine. One of its functions is to help initiate arm abduction (movement away from the body), such as when holding a briefcase slightly away from the body. It also stabilizes the arm in the joint, balancing the movement of the deltoids when the arms are at a 90-degree angle to the body. Due to its tendon’s position between parts of the shoulder joint (at the acromioclavicular or AC joint), it is prone to fraying, minor tears, and tendonitis, especially with poor posture like rounded shoulders—a common issue for computer users.
The infraspinatus muscle sits below the spine of the scapula (infra = below). It is responsible for externally rotating the shoulder, the motion we use to put on a coat sleeve or reach into the back seat of a car. It also helps stabilize the arm in the socket. This muscle often gets injured in baseball pitchers who, by throwing the ball at 90+ miles an hour, essentially throw their arm out of its socket. The infraspinatus acts as a brake that stops all that forward momentum. It is also susceptible to trigger points that refer pain to the shoulder and arm. In our practice, we often talk about not chasing pain, and this is a case in point. Pain at the front of the shoulder or vague aching pain down the arm, sometimes even into the wrist or hand (commonly mistaken for carpal tunnel syndrome), is often due to referred pain from trigger points in infraspinatus in the back of the shoulder. Massaging these points can be quite tender but very relieving.
The subscapularis is the largest muscle of the rotator cuff group, located under the scapula. Sandwiched between the rib and the scapula, this muscle stabilizes the scapula and keeps the shoulder in place. It also internally rotates the shoulder, the motion you do when pulling something across your body, like a bedspread. Subscapularis is a major culprit in frozen shoulder, a condition causing limited range of motion in the shoulder joint. Typical signs of a subscapularis issue include pain down the back of the arm and scapular area, coupled with a persistent ache in the back of the wrist.
Teres minor, the final muscle of the rotator cuff group, sits behind the armpit, adjacent to the infraspinatus. Its job is to stabilize the arm in the joint and assist with external rotation. This muscle tends to be the least injured of the four, generally only injured in very athletic individuals doing strenuous activity.
In our modern lifestyle of computer use, texting, driving, and TV watching, we tend to round our shoulders and shorten the muscles on the front of our body, particularly the pectoralis muscles in the chest and the biceps in the arm. These muscles cross the shoulder joint as well, inhibiting the muscles in the shoulder and back that counteract the forward pull. This imbalance can lead to a rounded shoulder posture and even impingement on various muscles, tendons and even nerves.
The best way to keep your rotator cuff healthy and happy is to pay attention to your posture, move your arm in all its ranges, and maintain a balance between the muscles of the upper back and front of the upper body. Regular massage therapy, yoga, pilates, physical therapy, and using proper form in personal training can support you in balancing these muscles, relieving pain, improving range of motion and becoming more aware of your posture. So, whether you're lifting weights, typing at your desk, or simply carrying groceries, remember to give your rotator cuff some love and care!
