The Importance of Shoulder Mobility (and How to Assess It)

We often take the shoulder for granted; from movements as simple as a shrug to a high velocity baseball pitch, the shoulder is a wildly capable joint essential to our everyday movement. (It actually has the greatest range of motion of any joint in the body!)

What’s unfortunate is that we don’t always acknowledge how complex the joint actually is. And without a thorough understanding of how it’s built and how it functions, there’s a higher likelihood for deficient biomechanics and gradual, functional limitations.

Shoulder stiffness and pain are both incredibly common issues, regardless of whether or not you lead an athletic lifestyle. (If you’ve ever caught yourself rolling your shoulders back to loosen them up, you know what we’re talking about.)

Let’s take some time to dissect what our shoulder joints are capable of, and how important a role mobility plays in our day-to-day.

Understanding the Shoulder Joint

There are plenty of reasons why shoulder mobility is important, but the easy answer is that your shoulders are involved in just about every upper body movement. Which is why ensuring full mobilization —including both flexibility and full range of motion — is key for maintaining peak functionality.

However! Understanding your shoulder mobility is more complex than it may appear; the joint itself has a lot of moving parts, and each impacts different facets of your overall shoulder movement.

Anatomy of the Shoulder Joint

Interestingly enough, while people refer to the shoulder as a singular joint, it actually consists of 4 smaller joints. (Who knew, right?) Let’s refer to a visual aid for this one:

As you can see, 2 of the joints (acromioclavicular and glenohumeral) are located at the primary joint that connects the arm to the torso, which is what most people picture when they think of the shoulder joint.

However, the other 2 joints (sternoclavicular and scapulothoracic) help us envision the true breadth of the shoulder. While we may not directly associate the collarbone or the shoulder blades with the joint itself, they actually play a major role in many of our everyday motions involving the arm and shoulder.

This is because the muscles that support the shoulder joint have connection points between many of these bony structures. Take the rotator cuff, for instance, which is the muscle group most commonly associated with the shoulder:

Your rotator cuff comprises 4 muscles that connect your scapula (the shoulder blade) to the humerus (the bone of your upper arm). We won’t go into complete detail about what each of these muscles are responsible for (that could be an entire article on its own), but in the grand scheme of things, these muscles help to stabilize the humerus within the glenohumeral joint.

Additionally, there are also several scapular muscles correlated with the back of the shoulder: 17, to be exact. Some of the most commonly discussed muscles are the lower and middle trapezius, as well as the serratus anterior:

This collection of muscles is also partially responsible for stabilizing the shoulder joint as a whole. Because the shoulder allows for a myriad of biomechanical movements, ensuring ample stability is essential to preventing injury within all of the tissues involved.

Speaking of biomechanics, let’s dig into the movements made possible by your shoulders!

Primary Biomechanics of the Shoulder Joint

There are a handful of basic motions that the shoulder joint is responsible for: flexion (moving your arms overhead), extension (moving your arms back behind you), horizontal abduction (lifting your arm up and away from your side), horizontal adduction (moving your arm back down to your side), and internal and external rotation (rotating your arm inwards and outwards, respectively).

But of course, as you can tell from the image here, these aren’t the only biomechanics available to the shoulder joint! From these 5 initial motions stems a complex range of combined functional movements.

Most functional movements of the shoulder combine linear motion (flexion or adduction) and some degree of rotation. For instance, when you want to move your arm behind the back and up towards the neck, you’re using a combination of extension and internal rotation. Or when you want to bring your arm across the front of your body, you’re recruiting both adduction and rotation.

And this is where mobility becomes vital. The glenohumeral joint (which is the connection point between the glenoid of the scapula and the head of the humerus) is a very shallow joint, akin to a golf ball sitting on a tee. This shallowness results in a limited amount of coverage between the ball and socket of the joint, meaning there’s more room for instability if the muscles aren’t pulling their weight.

So, when you mix and match these motions with various biomechanics, planes of motion, and level of activity, the shoulder has a lot of elements to account for. You have to maintain good mobility of this glenohumeral joint and its surrounding connective tissues to effectively tolerate movement without compensating or causing further pain.

Common Limitations at the Shoulder Joint

Unfortunately, with all the movement variety available at the joint, there are many circumstances that can negatively impact its ability to function properly. 

The 2 most common culprits for limited shoulder mobility are muscle weakness and muscle tightness.

With muscle weakness, the issues primarily arise within the 4 rotator cuff muscles or in one of the many scapular muscles. Because rotator cuff weakness causes instability of the joint, the shoulder will naturally recruit the deltoid muscle to compensate for lack of support. Unfortunately, while this may provide some degree of stability, it winds up limiting the mobility of your shoulder joint, particularly in regards to extension, flexion, and rotation.

(Conversely, some populations, like athletic pitchers, may actually sustain overuse injuries in the rotator cuff. Depending on how much strain is placed on certain portions of the shoulder, it’s possible to present highly specific, limited mobility with certain rotational movements.)

If you present weakness in any of the scapular muscles (particularly the low or mid trapezius or the serratus anterior), the shoulder will compensate by relying on the upper trapezius and rhomboid muscles. This can impact your ability to abduct or flex at the shoulder.

As for muscle tightness, people typically experience difficulty with the pectoralis minor or latissimus dorsi:

Per the left-hand image, the pectoralis minor (pec minor) connects the rib cage to the shoulder blade. If these muscles grow tight, they end up pulling the shoulder blade forward, limiting its ability to move properly. (For reference, simply lifting your arms overhead would require the shoulder blade to tilt backwards, so a tight pec minor could prevent you from achieving full flexion.)

Similarly, the latissimus dorsi (as pictured on the right) can grow tight and limit the scapula’s ability to move downward. This is because it connects directly to the humeral head, meaning any tightness will pull the humerus down and prevent that same overhead motion.

And of course, muscle weakness or tightness isn’t limited to just these 4 sets of muscles — any of the shoulder muscles can become impaired and negatively affect your mobility.


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How to Assess Shoulder Mobility

There are several means of testing your current mobility, some of which can be facilitated by yourself at home, and others that require the expertise of a physical therapist.

Shoulder mobility assessments can also be either active or passive. When working with a PT, they’ll likely prompt you to assess both aspects of mobility, just to get a full picture of what your shoulder joint is capable of.

Below are a few of the most common tests people facilitate. (While this isn’t an exhaustive list, they provide a good amount of variety between each.)

At-Home Shoulder Mobility Testing

This is one of the most accessible assessments: all you have to do is move your shoulder through all the different ranges of motion and assess how it feels.

(Quite literally just going through the motions!)

Granted, this method won’t yield specific results, and it’s not rooted in data-backed findings. But, it can still be quite insightful when you take the time to pay close attention to any restrictions, tightness, or pain that results from any of these everyday motions.

In this case, since you aren’t trying to pinpoint a particular diagnosis, the goal of this at-home assessment is to simply gauge what your shoulder is capable of relative to full range of motion in all directions.

(A common example of this kind of assessment is taking one arm, bending it at the elbow, and reaching above your head to touch the opposing shoulder. Then, bringing your arm back to the starting position, move into extension and bend at the elbow to touch the opposing shoulder again from below.)

Timing Test (Scapular Dyskinesis)

While the at-home testing is of course the easiest of assessments to facilitate, it doesn’t necessarily provide deeper insight into why certain motions may be limited.

For instance, the motion of bringing your arms overhead — as mentioned before, this requires the shoulder blade to move downwards and make room for the arm as it moves into extension.

Though this motion may not seem complex in our day-to-day, it actually requires a highly specific, coordinated pattern of biomechanics known as glenohumeral rhythm. Explaining the biomechanics can get a little nitty gritty, but the concept describes the coordination between your arm and shoulder blade. The tissues around the shoulder blade have to provide enough strength, stability, and mobility in order to effectively move the bony structures out of the way so the arm can extend and abduct as needed.

With this particular assessment, you’ll be prompted to raise your arms above your head against some kind of resistance. (Depending on what you’re seeking PT for, this could range anywhere from a resistance band to a kettlebell or weight.)

As you move your arms upward and over the head, the PT will observe the coordination of how your shoulder moves and whether or not its mechanics seem ideal. If the motions appear abnormal, it is often reported as “scapular dyskinesis,” or a deviation from the normal positioning of the shoulder blade through movement.

Strength Testing (Rotator Cuff)

This one is kind of a given, considering how weakened muscles are such a common culprit behind limited shoulder mobility. (After all, we aren’t going to simply identify muscle weakness and leave it to get worse!)

Strength testing is most frequently performed on your rotator cuff muscles, as they serve as the primary stabilizers for your scapula. Our particular clinic utilizes a dynamometer for measuring strength, and EMG sensors to assess how well these muscles activate, as well — your muscles can be as strong as they want, but they’re still ineffective if they can’t turn on properly to avoid compensatory mechanics.

(This image is not specific to the rotator cuff — though, it’s a solid example of demonstrating activation with the shoulder muscles.)

Once you and your PT are able to determine the specific strength and activation of these stabilizing muscles, you can hash out a plan for targeted strength training. This will allow you to regain optimal functionality through exercises that are completely tailored to your biomechanical needs.

Dust Off Your Shoulders!

If you didn’t know before, you know now: shoulder mobility can feel like a beast to figure out, but it’s an essential part of our everyday movement.

Understanding the complexity behind the shoulder joint and all its biomechanical functions is the first step to addressing any limited movement. From there, work through the different forms of mobility assessments to gain more specific insights into your limitations.

That’s when you can start exploring the types of exercises to alleviate your restricted movement! Part of the challenge to developing the right training program is that shoulder restrictions can be caused by either issues of limited mobility or limited range of motion — and making that distinction will determine what types of exercises are needed for proper recovery.

So, focus on first establishing what your limitations may be. Then, join us in our next blog reviewing some of the 10 best exercises that will address limited shoulder mobility or range of motion!

By Dr. Torey Page DPT OCS

Dr. Page is recognized as a specialist in evaluation and rehabilitation of the lower extremity, spine, and shoulder. He has had years of experience working as a physical therapist and as a strength and conditioning coach, so he is well-versed in the analysis of human movement and biomechanics (as well as advanced training in running mechanics and return to sport training). Torey has advised a wide range of clients, from sports teams to triathletes to the Woodside Fire Department. In his spare time, he enjoys spending time with his wife Joey, their beautiful daughter Savannah, and their dog Gatsby.

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