Rotator Cuff – Anatomy Highlight

Rotator Cuff Shoulder Muscles

Most people have at least heard the term “rotator cuff” at some point. If you’ve ever rehabbed from a shoulder injury, there’s a good chance you’ve even done exercises targeting it. Despite this general familiarity, most people don’t have a good understanding of what the rotator cuff actually is OR what purpose it truly serves in the body. This article will clear up all of that uncertainty!

Brief Shoulder Anatomy Lesson

Before I get into the details of the rotator cuff, let’s go through a high-level overview of basic shoulder anatomy. The shoulder consists of three bones and three-ish joints. I say three-ish because only two of them are true joints and one is not technically a joint, but is often referred to as one.

The three bones are the humerus (upper arm bone), clavicle (collarbone), and scapula (shoulder blade). The two true joints are the glenohumeral joint and acromioclavicular (AC) joint, while the third-ish joint is the scapulothoracic.

The Glenohumeral Joint

The main ball-and-socket joint of the shoulder is the glenohumeral joint. This joint consists of the head of the humerus (ball) and the glenoid of the scapula (socket). A unique feature of this joint is that the ball is significantly bigger than the socket, much like a golf ball resting on a tee. While this anatomical structure enables the shoulder to have the largest range of motion of any joint in the body, it also inevitably makes the joint less stable. Because of this inherent lack of bony stability, the shoulder is more reliant on dynamic muscular stabilization than any other joint.


The Acromioclavicular Joint

This joint is a plane style joint, connecting the outside end of the clavicle to the acromion of the scapula. It is made up of two relatively flat surfaces separated by a fluid-filled space and held together by strong ligaments. Its structure allows the joint surfaces to glide past one another in multiple directions. The main function of the AC joint is to allow for motion of the scapula while connecting the shoulder to the body. The AC joint is actually the only true joint connecting the arm to the rest of the body!


The Scapulothoracic Joint

Although the scapulothoracic joint is not a true joint, it can be helpful to think of it as one. It represents the junction between the scapula and the thorax. While it has no joint fluid, capsule, or ligaments, it does function much like a joint. The scapula is able to slide up, down, and side-to-side. Additionally, it can rotate or tilt in multiple planes. Since the glenoid (socket of the glenohumeral joint) is located on the scapula, this ability of the scapula to move contributes even more mobility to the shoulder. With no direct ligamentous support, the scapulothoracic joint is completely reliant on dynamic muscular stability and the integrity of the AC and SC (sternoclavicular) joints on either end of the clavicle.


What is the Rotator Cuff, Really?

The rotator cuff is a group of four muscles. These muscles are located in the shoulder, all originating on the scapula and inserting on the humerus. The four muscles are the supraspinatus, infraspinatus, subscapularis, and teres minor.


The supraspinatus originates on the upper part of the back of the scapula. The smallest of the rotator cuff muscles, it wraps around the top of the humerus and inserts on its outer aspect.



The infraspinatus originates on the middle part of the back of the scapula. It wraps around the rear of the humerus, inserting on the back of its outer aspect.



The subscapularis originates on the front surface of the scapula (between the scapula and the rib cage). The largest and strongest of the rotator cuff muscles, it wraps around the front of the glenohumeral joint, inserting on the front of the humerus.


Teres Minor

The teres minor originates on the back of the scapula – below the origin of the infraspinatus. It then passes around the back of the humerus, inserting on its outer surface.


What does the Rotator Cuff do?

While the name of the rotator cuff offers a clue into one movement produced by some of the muscles, the moniker can also be misleading. Although the rotator cuff muscles can produce rotation of the glenohumeral joint, this is not their primary function. Their chief purpose is actually to stabilize the shoulder during movement, ensuring that the head of the humerus stays centered in the glenoid. They achieve this goal through coordinated, simultaneous action.

When the rotator cuff is injured or weak, it leads to instability in the shoulder. This instability in turn causes pain, decreased range of motion, and reduced ability to exert force in nearly any direction with the affected arm. Therefore, it is crucial to maintain strength and coordination in all the muscles of the rotator cuff.

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How can you Train the Rotator Cuff?

There are a number of ways to train the rotator cuff. I will go through three options in this article:

  1. Closed Kinetic Chain (CKC) Stabilization Training (with the hand planted)
  2. Rotational Strength Training
  3. Full-Range Motor Control Training

1. Closed Kinetic Chain Stabilization

For this exercise, you’ll start in a pushup position with your feet roughly hip width apart. Your hands should be directly beneath your shoulders, fingers spread wide, and index fingers pointing forward. Keep your shoulders active, pushing the ground away so that your shoulder blades are moderately protracted (spread apart). Focus on maintaining strong activation of the abdominals, drawing your belly button in toward your spine and keeping your lower back flat with a posterior pelvic tilt (tailbone tucked).

The first and easiest version of this exercise is simply holding this position. You can start with short holds of 5s and gradually build up to holds of 20-30s.

Once that feels easy, you can introduce some weight shifts side to side. Do this by unweighting one hand at a time as much as you are able without losing stability or moving your body to compensate. Shift weight from one hand to the other at your own pace for 20-30s.

A natural progression from these weight shifts is to fully unweight one hand at a time, lifting it from the floor. You can start by lifting your hand in place. Next progress to lifting it up and tapping the other hand, then the elbow, and finally the shoulder. Again, the most important piece here is maintaining stability and not allowing your body to move as a counterbalance. 20-30s at your own pace is a good guide for this version as well.

Check out this video to see the exercise. The guy in the video is moving his body too much as a compensation, focus on using more control.

2. Rotational Strength Training

Since weakness of shoulder external rotation is more commonly a source of shoulder pain than weakness of internal rotation, we will focus on that motion in this article. External rotation exercises also strengthen the supraspinatus, infraspinatus, and teres minor (3 out of 4 of the rotator cuff muscles), so you’re getting the most bang for your buck here.

The exercise we’ll go through today is called “No Monies”. You’ll need two rolled up towels, a light resistance band, and a wall. Start by placing the towel rolls under each arm. This creates space in the shoulder joint and allows for strong muscle activation. Lean back against the wall so that your hips and shoulders are both resting on the wall. Keep your elbows back so that they rest lightly against the wall.

Next, with your elbows bent to 90°, grip the resistance band with both hands using an underhand grip. Keeping your elbows against the wall and the towel rolls trapped between your upper arms and rib cage, pull the band apart by rotating both arms outward simultaneously. Make sure that your elbows maintain an angle of 90° throughout, moving your hands upward slightly as you pull to accommodate for the angle of your upper arm created by the towel rolls.

Use a smooth, controlled motion throughout the external rotation movement and the return to the starting position. Aim for 2-3 sets of 15-20 repetitions. These muscles are designed to work at a low level in the background for stability, so this is not the time to get an ego and go heavy.

Check out this video for an example. The cues in the video say to pull your shoulder blades together, but you really should keep the shoulder blades stationary and rotate your upper arm to create the movement.

3. Full-Range Motor Control Training

Since the rotator cuff primarily functions to create stability in the shoulder, it is important that these muscles fire in a coordinated manner throughout the entirety of your available range of motion. You can work on this control using an exercise called Controlled Articular Rotations (CARs). CARs come from a system called Functional Range Conditioning and are designed specifically to build full range control. As you move through this exercise, you maximally stimulate receptors in the joint that tell your brain where your joint is in space. Simultaneously, your brain is sending information to the muscles. The integration of these two information exchanges creates optimal motor control.


Stand with your feet about hip distance apart and start by creating tension throughout your body, tightening all the muscles from head to toe. Aim for a contraction of around 40% intensity to start. This full-body tension taps into a neuromuscular phenomenon called irradiation. Irradiation refers to the fact that when you contract a muscle in one area, you get a stronger contraction of all the muscles around it. As an example, try clasping your hands together. Now squeeze, starting as light as possible and gradually building up until you are squeezing hard. Notice that as you ramp up the intensity of your squeeze, more and more muscles in your body start to work. Now, focus on contracting all the muscles in your body as you squeeze. See how you are able to output more force when you activate throughout the body? That’s irradiation.

The Movement

Make a fist with one hand and open your other hand with the palm facing forward. Now slowly start to raise your arm out in front of you, moving slightly across your body and rotating the whole arm internally. By the time your arm is fully overhead, your palm should face away from and your elbow behind you. Continue this same movement, now reaching behind you and still rotating the whole arm inward. You should end with your arm by your side, your hand facing away from your hip, and your elbow pointing forward. Now, reverse the whole movement until you end up where you started.

As you move, maintain as much muscle activation as you can. The movement should be slow and controlled. Imagine that you are pushing your way through peanut butter. There should be no pain. Only move through as much range as you can with no pain. If you do experience pain at some point in the motion, move around the pain rather than pushing through it.

Check out this video to see the movement.

In Closing

Armed with this information, you should have a better understanding of the rotator cuff than the vast majority of people. To sum things up, the rotator cuff is a group of four muscles that is primarily responsible for stabilizing the ball of the shoulder joint in its socket during movement. The structure of the shoulder enables an incredible amount of mobility, but comes with heavy reliance on the muscles for stability. This stability requires adequate strength and coordinated action in all four of the rotator cuff muscles.

The exercises described in this article will help you build strength, stability, and full-range motor control. While they are not going to solve every rotator cuff problem, they offer a great starting point. These exercises and this article are intended to be educational and should be used only in the absence of pain or injury. If you have pain or have sustained an injury, you must seek evaluation by a doctor of physical therapy to determine the appropriate course of action.

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Health Advice Disclaimer

This article provides example exercises that are applicable to many, but not all people.  They are based on typical presentations seen in my personal clinical practice.  These exercises address common deficits found in the population discussed, but can in no way take the place of professional evaluation and treatment by a licensed medical practitioner.  It is impossible to provide 100% accurate diagnosis or prognosis without a thorough physical examination and likewise the advice given for management or prevention of any injury cannot be deemed fully accurate in the absence of this examination. 

There should be no pain during any part of this program aside from a normal muscle “burn”.  If you are currently experiencing any pain or injury, seek professional evaluation before undertaking this or any exercise program.  Ensure that you are medically cleared for exercise before undertaking this or any exercise program.  Significant injury risk may occur if you do not seek proper evaluation.  No guarantees of specific outcome are expressly made or implied in this article. 

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