Why The Rotator Cuff is So Important to Understand

  • Health Education   •   Oct 27, 2021

By Megan White, RMT

4 Minute Read


hen it comes to the shoulder there are some misconceptions. Did you know that the shoulder is designed primarily for mobility, and because of its design, the shoulder joint is one of the most unstable joints in the body? Did you know that the shoulder is actually made up of two joints, once being one of the must unique joints in the body? Let’s dive into the shoulder so that you understand how complex and important this piece of anatomy is.

There is more than one place that the shoulder connects to the body; the actual shoulder joint, which is the first one you think of called your glenohumeral joint. This joint is a ball in socket type joint where the humerus (arm bone) connects to the glenoid fossa of the scapula (shoulder blade). The socket of his joint is the most shallow socket of all of the ball-in-socket joints in the body, which contributes to the extreme limits of range of motion in the shoulder. However, that extreme range of motion and minimal stability around the joint also makes the shoulder joint very susceptible to dislocations.

The other joint related to the should is not actually a true joint but it is where the scapula ‘articulates’ with the underlying rib cage, also referred to as a pseudojoint. This is called the scapulothoracic joint. The shoulder blade is held flush along the back of the rib cage through muscular attachments with the levator scapula, rhomboid minor and major, and trapezius muscles. In conjunction with the muscles of the chest and shoulder joint, the shoulder blade glides upwards, downwards, forward (protraction), and backwards (retracted). This unique movement pattern of the scapula has direct impacts on the position of the shoulder joint and is ultimately closely correlated with biomechanical effects to and from upper body posture.

Now that we know about those two joints in the shoulder, how about the muscles that function in the shoulder.

Most people call the muscles of the shoulder the “rotator cuff” muscles. So what are those muscles and how do they move the shoulder?

The acronym S.I.T.S can be used to remember the muscles of the rotator cuff.  The first ‘S’ stands for  Supraspinatus, which lies on top of the scapula, attaches to the upper part of the humerus, and is responsible for abduction of the shoulder/arm (lifting the arm away from the side of your body). The infraspinatus and teres minor are the next two muscles. Infraspinatus is the larger of the two muscles, lies on the backside of the scapula, and attaches to the upper humerus. Teres minor is a smaller muscle and starts in the outer edge of the scapula and also attaches to the humerus. Both of these two muscles together bring the shoulder/arm into external rotation (or rotating the arm outwards). The last muscle ‘S’ brings the shoulder/arm into internal rotation.  Subscapularis, sits on the front of the scapula behind the rib cage, attaching to the head (upper portion) of the humerus. What’s unique about the interdependent relationship between each of the four rotator cuff structures is that as a whole, the set of muscles and tendons also provide much of the stability to the shoulder joint, since the joint is already quite unstable due to the flatness of the socket. So when one or two of the rotator cuff tendons are injured, the shoulder joint’s stability is compromised leading to further dysfunction and risk of additional injury and pain.

These four muscles are the main muscles of the rotator cuff and can be a source of pain and injury, from a number of different mechanisms. Any time the shoulder is dislocated, or injured in any sport involving shoulder movements, one or more of the SITS muscles can be torn. More commonly, these muscles can also be injured from repetitive, overuse and postural syndromes, where dysfunction and inflammation slowly builds in the muscles and tendons over time (tendonitis). These are typically the types of shoulder problems we see in clinical practice, because as previously mentioned, they often relate to poor posture in the upper back and symptoms tend to come on gradually. It also requires the proper education and knowledge on how to make the postural improvements in order to correct the underlying cause of the shoulder pain.

If you’ve injured your rotator cuff with either a strain, a dislocation, or tendinitis from repetitive stress what do you do? The vast majority of these injuries can be managed and treated using conservative therapy options. In the acute stage pain, when the pain is new and it’s difficult to move the shoulder or sleep on that side of your body, your best measure to combat the pain and the associated inflammation in the tissues is by applying ice over the affected area. Once the healing has started and its easier to move the shoulder joint with less pain, massage therapy can help the muscle fibres heal quicker and more efficiently. Massage therapy can help guide the scar tissue to lay down appropriately, encourage or maintain the muscle length, remove any trigger points or knots formed and keep the shoulder moving correctly.

Once the shoulder can move within its normal range of motion with little to no pain light stretching can be applied to keep the SITS muscles to their original length to prevent problems in the future. You’ll want to stretch supraspinatus by pulling your arm across your chest, stretch infraspinatus and teres minor by guiding the back of your hand to your low back. Subscapularis can be stretched by externally rotating the humerus, do this by standing next to the doorframe and reaching out and placing the inside of your forearm parallel with the doorframe, then take a step forward. This places your shoulder into external rotation which is the opposite action of these two muscles, therefore stretching it.

There are other muscles that attach to the shoulder that are not included in the rotator cuff, they include the pectoralis major and the deltoid muscles. The deltoid muscle is the one on the top, the one that makes the shoulder look round and muscular, and is the primary driver of abduction past 15º away from the body (such as reaching overhead). It is also responsible for flexion (reaching arm up out front) and extension (reaching arm behind) of the shoulder/arm. Pectoralis major is your bench press and push-up muscle, the one everyone shortens to ‘pec’. It makes up the bulk of the chest muscle and is responsible for flexion, adduction, and internal rotation of the shoulder/arm.

Many people, especially those with computer jobs, suffer from pain, snapping, or grinding underneath the shoulder blade. This is called “snapping scapula syndrome’ also called scapulocostal syndrome. This condition is caused by atrophy and splaying of the subscapularis muscle, bringing the shoulder blade very close to the surface of the ribcage. Along with the subscapularis, the pectoralis major is usually involved in this condition. However, the pec major muscle is usually contracted and is pulling the shoulder forward, making it very difficult to correct the dysfunction happening in subscapularis.

If you or someone you know suffers from these kinds of shoulder problems and poor posture is likely in play, we have solutions! Massage therapy mixed with a plan of stretching and strengthening can help revert the scapulocostal syndrome and regain balance within the shoulder. A massage therapist can help release the contracted pectoralis major, activate and strengthen the atrophy of subscapularis, and help you to bring muscle balance back to the shoulder with a home care plan. Reach out via email (info@activeapproach.ca) or visit us online to submit your questions – we are here to help you Get Back To Your Active Life!

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