Importance Of The Shoulder Blade For Shoulder Function

Remember shoulder impingement from last week? Well, the scapula (shoulder blade) has a HUGE influence on how the shoulder functions and moves. The scapula is stabilized by four main muscle groups on the thoracic (rib) cage. From there, all four rotator cuff muscles come off the scapula to stabilize the shoulder joint so the shoulder can move and function without pain. If one or more of the muscles that stabilize the scapula isn’t doing its job, scapular winging can occur and lead to things like shoulder impingement and pain over time.   

The scapula only has one true bony attachment to the rest of the skeleton and that’s through the clavicle (collarbone) attaching to the sternum. Otherwise, it’s basically floating in space. That’s why it’s so important that the muscles stabilizing and holding the scapula on the rib cage are functioning properly. The four main ones include the serratus anterior, rhomboids, trapezius, and levator scapulae. When these muscles are doing what they’re supposed to do, the rotator cuff muscles can effectively stabilize the glenohumeral (shoulder) joint.

If the rotator cuff muscles weren’t there, the big deltoid muscles of the shoulder would take over and the arm would just jam up into the socket every time we’d try and lift it up. The rotator cuff counteracts the delts by depressing the arm in the glenohumeral joint when we elevate the arm so it stays stabilized in the joint. That way jamming doesn’t occur and impingement and pain are prevented.

The scapula and shoulder work as one functional unit. The scapula acts as a stable base so the shoulder can be mobile as we know it. But what if there’s a weak link in the chain? (For the purpose of this discussion we’ll say there’s been no trauma, rotator cuff tear, neurologic injury, or severe arthritis) Most commonly there’s a muscular imbalance in the scapular stabilizing muscles where one or two are dysfunctional or not doing their job and the others are compensating and working overtime to stabilize and prevent pain from happening.

The two usually underperforming are the serratus anterior and lower trapezius (there’s an upper, middle, and lower trap) but the serratus is usually the bigger issue. The upper trapezius and levator may take over to help stabilize, which could be contributing to the tightness and tension you tend to carry in your neck and upper back. Over time this can lead to scapular winging (aka scapular dyskinesis) and now what?

Stabilization is thrown off, shoulder movement becomes inefficient, and risk of injury, impingement, shoulder capsule, and rotator cuff problems all rise. Obviously, we don’t want that! Check out the video to see some scapular winging tests and exercises you can do at home!

-Ryan Donahue, DC

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