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My Shoulder Can't Dance: Shoulder Mechanics 101

Shoulder pain is a common and frustrating musculoskeletal issue for many athletes and non-athletes alike. It has been reported that shoulder injuries make up 60% of CrossFit related injuries. Even in a typical population the prevalence of rotator cuff injuries is between 20-22% at any given time. This just goes to show that shoulder pain, dysfunction, and injury are common in all walks of life and at different ages and stages.

Obviously, the cause of shoulder pain can vary greatly. There are certainly traumatic causes, as well as labral and rotator cuff tears that can be very significant and surgical. However, most shoulder injuries are not traumatic and acute. Most shoulder injuries are injuries that develop over time. These are largely driven by abnormal or poor mechanics that lead to increased stress on tissues over periods of time and lots of training/life reps.

When your shoulder is functioning optimally 1/3 of your overhead motion doesn’t come from your shoulder joint at all. Instead, this portion of movement comes from your scapular upward rotation. This rotation allows full expression of overhead mobility and stability as well as optimal performance. When scapular mechanics and motion are compromised, they can have a significant negative effect. Instead of rotating upward and creating space beneath your acromion (bony prominence on top of shoulder), a lazy scapula can cause compression of the bicep, rotator cuff, and sub-acromial tissue leading to pain and irritation. Over time this can worsen and even lead to tendon fraying and further damage.

Let’s break down big 3 of scapular mechanics:

When thinking about scapular mechanics there are three muscles that should be a primary focus. Obviously, there are other muscles involved in small amounts but these three are as essential as Jordan, Pippen, and Rodman were to the 90’s Chicago Bulls. Each fundamentally different in their role, but important to functional success.

The big 3:

1. Upper trapezius

2. Serratus anterior

3. Lower trapezius

Since these muscles attach to different edges or parts of the scapula, when they contract in unity the result is a nice upward rotation of the shoulder blade. You can visualize this from the picture below.

Unfortunately, when one of these muscles is weak or not firing appropriately the result is scapular movement dysfunction. If unchecked for long enough, this can lead to a myriad of symptoms.

Let’s look at a real life example.

The picture on the top shows the mid phase of scapular movement as this patient moves their arms overhead. At this point, everything looks relatively good and symmetrical.

The picture on the bottom paints a very different story. As the patient gets arms fully overhead, you can see some obvious problems in mechanics arise. On the right scapula, you see excellent activation, a flatter angle, and tons of tissue bulging to the side showing good forward movement. On the left scapula, you see less activation, a steeper angle, and no tissue bulge. You can also notice how much higher the left shoulder rises than the right.

What does this mean?

This means that Rodman is partying in Vegas. Jordan is playing baseball. Only Pippen is left of the big 3 and we all know Scottie isn't much without his squad. The patients left upper trap is firing, but the other two muscles are not even on the court. That is why you see upper trap cause the shoulder to rise, but little scapular movement. It takes all three firing in unity. No exceptions. This is the reason this patient is having significant left shoulder pain when lifting overhead. It’s a story I’ve seen painted in muscular tissue a thousand times over.

So the big question is: “What can I do about it?” You have to teach your shoulder to dance.

The fix is very simple, but not easy. It takes time and a lot of effort. You have to recruit and strengthen the weaker lower trap and serratus anterior. Once you’ve done this, you also have to teach them to work together. This can be the tough part. Here are a couple key exercises that I commonly use for patients that present with this problem.

1. Serratus pike press up

2. Shoulder ER with press

3. Y’s and 90/90 press

4. Serratus wall slide

Scapular dyskinesis is common and in of itself is not a huge problem. The problem arises after thousands of lifts, reps, and acts of daily life. You can’t run away from mechanics, they’ll always catch up to you. Let’s be proactive. Let’s build scapular strengthening into our current fitness plan. Let’s keep these injuries from ever happening. What do you say?

Stay Kinetic Friends.


Dr. Levi Kerby is a physical therapist, orthopedic certified specialist, and owner of Kinetic Performance and Rehab in Winston-Salem, NC. He enjoys fly fishing, guitar, various forms of fitness, and treating active and motivated individuals.

If you're dealing with an injury or pain, you can contact Kinetic Performance and Rehab directly below.

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