Rotator Cuff: What It Actually Does, Why It Gets Angry, and What You Can Do About It

Since tearing part of my supraspinatus tendon, I’ve had a pretty good reason to spend even more time digging into shoulder anatomy.

Which is probably exactly what somebody who already likes anatomy needed.

Another rabbit hole.

The rotator cuff gets talked about a lot, but I think a lot of people picture it as one structure.

It isn’t.

It’s a group of four muscles and their tendons that work together to move and stabilize the shoulder.

And once you start looking at how the shoulder actually works, you realize pretty quickly that the rotator cuff is only part of the story.

First: What Is the Rotator Cuff?

The four rotator cuff muscles are:

• Supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

A common way to remember them is SITS.

These muscles originate on the scapula and their tendons attach around the head of the humerus, creating the “cuff” around the shoulder joint.

Their job is not just to move the arm.

They also help keep the humeral head centered in the relatively shallow socket of the shoulder while larger muscles move the arm.

That stability part is important.

The shoulder gives us a huge amount of mobility, but the tradeoff is that it doesn’t have the same deep bony stability as something like the hip.

So a lot of shoulder stability has to come from muscles, tendons, the joint capsule, labrum, and coordinated movement.

Basically, your shoulder has a lot of freedom.

It also has a lot of opportunities to complain.

Supraspinatus

This is the one I have become much more personally acquainted with.

The supraspinatus sits above the spine of the scapula and attaches to the greater tubercle of the humerus.

It helps initiate abduction—raising the arm out to the side—and it also contributes to stabilizing the humeral head in the socket.

It is supplied primarily by the suprascapular nerve, with most of those nerve fibers coming from the C5 and C6 nerve roots in the lower neck.

In my case, this is the tendon that has the partial tear near its attachment at the humerus.

So naturally I have now read far more about the supraspinatus than I ever planned to.

Infraspinatus

The infraspinatus sits below the spine of the scapula.

Its big job is external rotation of the shoulder—turning the arm outward.

It also helps stabilize the humeral head.

Like the supraspinatus, it is supplied by the suprascapular nerve.

If you’ve ever done one of those band exercises where your elbow is tucked against your side and you rotate your forearm outward, the infraspinatus is one of the main muscles being trained.

It is not a very dramatic movement.

Rotator cuff rehab seems to contain a lot of movements that look like absolutely nothing until you are the person whose shoulder is injured.

Then suddenly they are very interesting.

Teres Minor

Teres minor is another external rotator.

It is smaller than the infraspinatus but helps with external rotation and shoulder stability.

Unlike the supraspinatus and infraspinatus, teres minor is supplied by the axillary nerve, mainly from C5-C6.

That same axillary nerve also supplies the deltoid.

So when shoulder symptoms involve significant weakness, muscle wasting, or altered sensation, it is another reminder that not every shoulder problem is simply a tight muscle that needs to be rubbed.

Subscapularis

The subscapularis is the odd one out because it sits on the front surface of the scapula.

Its main actions include internal rotation and adduction of the arm, and it contributes significantly to shoulder stability.

It is supplied by the upper and lower subscapular nerves, primarily from C5-C7.

If the infraspinatus and teres minor are helping turn the arm outward, the subscapularis is one of the big players pulling the other direction.

The shoulder works because these muscles balance each other.

Not because one of them wins.

The Rotator Cuff Doesn't Work Alone

This is where shoulder problems start getting more interesting.

The rotator cuff may be injured, but the rest of the shoulder does not simply stop participating.

Other muscles start doing more.

Movement changes.

People guard.

Posture changes.

Range of motion changes.

And suddenly the original problem may be creating several secondary ones.

Some of the other important players include:

Deltoid — one of the major muscles responsible for lifting the arm.

Trapezius — helps control the scapula.

Serratus anterior — extremely important for upward rotation and movement of the scapula against the rib cage.

Rhomboids — help retract and stabilize the scapula.

Pectoralis major and minor — influence shoulder and scapular position.

Latissimus dorsi — contributes to extension, adduction and internal rotation.

Biceps, particularly the long head — crosses the shoulder and can become a source of anterior shoulder pain.

Then you have the joint capsule, labrum, bursa, AC joint, clavicle, scapula and thoracic spine all participating in what we casually call “the shoulder.”

Simple.

Except not really.

The Scapula Matters More Than Most People Think

Your shoulder blade is not just sitting there.

Every time you raise your arm, the scapula has to move too.

It upwardly rotates, tilts and glides across the rib cage while the humerus moves in the glenoid.

That coordinated movement is one reason shoulder rehabilitation often involves more than just strengthening the rotator cuff.

If the scapula is not moving well, the muscles controlling it may need attention too.

That is where muscles like the serratus anterior and trapezius start becoming especially important.

And it is also why somebody can have shoulder symptoms and feel tightness or fatigue around the upper back, neck and shoulder blade.

The body is very good at finding another way to accomplish a movement.

Whether that substitute movement is a good long-term strategy is another question.

Then There Are the Nerves

This is another reason shoulder pain deserves more thought than:

“My shoulder hurts. Massage the shoulder.”

The supraspinatus and infraspinatus are supplied by the suprascapular nerve.

Teres minor and the deltoid are supplied by the axillary nerve.

Subscapularis is supplied by the subscapular nerves.

Most of those nerve fibers trace back to the C5 and C6 spinal nerve roots in the neck—the fifth and sixth levels of the cervical spine.

That matters because problems in the neck can sometimes refer pain into the shoulder or create weakness, numbness, tingling, or altered sensation that looks like a shoulder problem.

And this was actually part of my own workup.

I injured my shoulder at work on July 28 and went to the clinic that same morning to have it evaluated.

At that point, the shoulder itself was obviously the main problem.

Later that same day, toward the end of my shift, my right hand started swelling.

Then I started losing sensation across the back of the hand.

That got my attention pretty quickly.

Pain in the shoulder is one thing.

Swelling farther down the arm combined with changing sensation is something else.

So later that same day, I went to the emergency room.

They did a CT scan to make sure there wasn’t a vertebral or other bony problem in the cervical spine that could be contributing to the symptoms or possibly affecting a nerve.

The CT did not show anything abnormal that explained what I was experiencing.

That was important too.

It helped rule out an obvious bony problem in the neck as the source of the symptoms.

The swelling and loss of sensation were ultimately attributed to the amount of inflammation and swelling around the shoulder, including the bursa.

At the time, though, they still needed to make sure there wasn’t something else going on.

Almost a week later, I had the MRI.

That was the imaging that finally showed the partial supraspinatus tear and gave a much clearer picture of what had actually happened in the shoulder.

That whole process was a good reminder for me that medical imaging does not always give you the answer on the first try.

Sometimes one test rules something out.

Another test looks at a different type of tissue.

And eventually the pieces start fitting together.

It also reinforced something I think is important when looking at shoulder problems:

Where somebody feels a symptom is not always where the entire problem starts.

And once numbness, tingling, altered sensation, unusual swelling, or significant weakness enters the picture, it is no longer just a question of which muscle might be tight.

It Isn't Always the Rotator Cuff

This is another thing I think gets oversimplified.

Shoulder hurts?

Must be the rotator cuff.

Not necessarily.

Other possibilities can include:

• Biceps tendinopathy

• Subacromial or subdeltoid bursitis

• AC joint problems

• Adhesive capsulitis, better known as frozen shoulder

• Glenohumeral arthritis

• Labral injuries

• Cervical spine problems

• Nerve irritation

• And sometimes multiple things at the same time

Frozen shoulder in particular can create significant pain and loss of both active and passive range of motion.

Rotator cuff problems more commonly preserve passive range of motion even when active movement hurts or becomes weak, although real people do not always read the textbook before getting injured.

That is part of why diagnosis matters.

What Can Happen When the Rotator Cuff Isn't Working Well?

The obvious problem is shoulder pain.

But that can lead to a whole chain of secondary issues.

You may stop raising the arm normally.

You may shrug more.

The upper trapezius may start working overtime.

The neck may get tighter.

The pecs may start feeling restricted.

The scapula may move differently.

Reaching behind your back may become difficult.

Sleeping on that side may become miserable.

That one has been especially true for me. I am a side sleeper, and apparently my sleeping brain still thinks my injured right shoulder is the preferred landing spot. I will roll onto it during the night, wake up because the shoulder is not amused, move off it, and then apparently forget the entire lesson a few hours later.

You may start using the other arm for everything.

That has been one of the more annoying parts for me. My left shoulder apparently got promoted to doing the work of two shoulders without being consulted first, and lately it has been filing its complaints in the form of soreness.

And if the shoulder stays guarded and stops moving for long enough, stiffness can become its own problem.

I got a pretty good example of that last weekend. I drove to Suttons Bay to pick up a new pair of cycling shoes—which is a completely different rabbit hole—but on the way back my right arm started getting increasingly annoyed.

By the time we got back toward Gaylord, changing the radio station was becoming a project. By the time we got home, I couldn’t shift the car into park or even turn it off with my right hand.

I can’t say exactly how much of that was guarding, holding the arm in one position for hours, fatigue, or some combination of all three. But the change over the course of one drive was hard to miss.

That is one reason I am becoming increasingly interested in what happens around an injury, not just at the exact structure that was injured.

Mobility: Keep the Shoulder Moving, but Don't Force It

This section needs a big disclaimer.

If you have an actual shoulder injury, especially a tear, recent surgery, instability or significant pain, your doctor or physical therapist should be the one deciding what is appropriate for you.

These are examples of movements commonly used in shoulder rehabilitation, not a personal rehab prescription.

Pendulums

These are about as exciting as they sound.

Lean forward, let the arm hang and use gentle body movement to create small circles or swings.

The idea is movement without asking the shoulder to produce much force.

Assisted Shoulder Flexion

This can be done with the opposite arm, a stick, or sometimes by sliding the hands forward on a surface.

The stronger side helps move the involved arm.

Wall Slides

Place the hand or forearm on the wall and gradually slide upward as tolerated.

Again, the point is not to win a wall-sliding competition.

It is controlled movement.

Gentle External Rotation

Depending on the injury, assisted or active external rotation may be used to maintain or restore motion.

Thoracic Mobility

The shoulder blade sits on the rib cage.

If the upper back barely moves, the shoulder may have to compensate.

Thoracic extension and rotation work can sometimes be an important piece of the bigger picture.

Strength Training: Usually Boring Before It Becomes Impressive

Exercise is a central part of conservative management for many rotator-cuff-related shoulder problems, although the exact type, intensity and progression varies considerably from person to person.

Some common categories include:

Isometric External Rotation

Push outward against an immovable surface without actually moving the arm.

This is one of the things I am currently doing in PT.

It does not look impressive.

It still counts.

Isometric Internal Rotation

Same idea, opposite direction.

Isometric Abduction

Gently pushing the arm outward into a wall or other resistance without allowing actual movement.

Band External Rotation

Usually performed with the elbow near the side while rotating the forearm outward against resistance.

Rows

Rows help strengthen the muscles around the scapula and upper back.

Serratus Exercises

These can include wall slides, serratus punches and other variations intended to improve scapular control.

Scaption

This is raising the arm in the plane of the scapula—slightly forward from directly out to the side.

It is often used during shoulder strengthening because that plane tends to work well with normal shoulder mechanics.

Eventually, depending on the injury and the person's goals, strengthening can progress toward heavier resistance and overhead activity.

But rehabilitation is progression.

Not:

“My shoulder felt better this morning, so I added 40 pounds.”

I am mentioning that mostly for myself.

Where Massage Fits

This is obviously the part I pay a lot of attention to as a massage therapist.

Massage cannot reattach a torn tendon.

It cannot diagnose a tear.

It cannot replace physical therapy.

And if somebody has a serious shoulder injury, I do not want them coming to me instead of getting the shoulder evaluated.

But that does not mean massage has no role.

Where I think massage can make sense is in addressing everything around the injury.

The upper trapezius that has been working overtime.

Pecs that have become guarded.

Posterior shoulder muscles that feel constantly tight.

Lats that may be limiting movement.

Neck muscles that are compensating.

The opposite side that suddenly has to do everything—and may start getting sore from carrying the extra workload.

Even muscles farther down the arm may start working differently because somebody is protecting the shoulder.

That is where massage can potentially help reduce discomfort, improve short-term movement tolerance and make the person feel better while the actual rehabilitation work continues.

The key word there is alongside.

Not instead of.

Massage Should Also Know When to Leave Things Alone

Sometimes the best thing a massage therapist can do is recognize when something does not belong on the massage table.

• Sudden major weakness

• Loss of the ability to raise the arm after an injury

• Significant trauma

• Numbness or tingling

• Progressively worsening symptoms

• Unexplained severe pain

• Major loss of range of motion

Those deserve evaluation.

My own injury is a good example.

I felt a small pop.

It didn't initially hurt much.

Then a few minutes later I couldn't lift my arm.

That was not a “maybe I just need my trap worked on” situation.

The Bigger Lesson for Me

Before my own injury, I obviously knew the four rotator cuff muscles.

That was part of massage school.

What has become much more interesting is seeing how quickly one injured structure changes everything around it.

The way you move.

What muscles start compensating.

What activities become difficult.

What you stop doing.

What gets tight.

What gets weak.

And how much of rehabilitation is figuring out what you can continue doing while the injured area gradually regains capacity.

That is probably the biggest thing I want to carry into my massage practice.

I don't want to look at somebody's painful shoulder and only think:

“Which muscle hurts?”

I want to think:

What happened?

What movements are limited?

What has started compensating?

What are they trying to get back to?

What is appropriate for massage?

What belongs in physical therapy?

And is there anything here that needs medical evaluation before I put my hands on it?

The rotator cuff may only have four muscles.

The shoulder problem usually involves a lot more than four muscles.

Apparently the deeper I get into this, the less simple shoulders become.

Which probably means I’ll keep digging.

Endless Path and Wellness
www.endlesspathwellness.com

This article is educational and based on anatomy, current research and my own experience with a shoulder injury. It is not a diagnosis or an individual rehabilitation program. Shoulder pain can come from several different structures, and exercises that are appropriate for one injury may not be appropriate for another. Significant trauma, weakness, loss of motion, neurological symptoms or persistent pain should be properly evaluated.