Winging It: Scapular Instability

In the past we have talked about the importance of our posture and our rotator cuff muscles but we really haven’t talked about how they are connected yet. Pretty much everyone can identify their shoulder blade (“Scapula”) but can you say what it is for? It’s a weird flat bone that sits on your upper back and just kind of floats there, but everything in the body has a purpose (except for those wonderful vestigial organs like the appendix). The scapula’s purpose is to act as an anchor to the arm. It holds the ends of the rotator cuff muscles as well as the Biceps, Triceps, and the Deltoid muscles. Now what is the most important aspect of an anchor? That’s right! Stability! Just like our core muscles, our shoulder blades should remain rock solid when we need them but still have some mobility to adapt to changes in arm movement and pressures.

So how can a flat bone be both stable and mobile at the same time? The scapula sits on top of the rib cage with a connection to the collar bone (“Clavicle”) at the front. This connection should not provide mechanical support but only act as a guide for the position of the scapula relative to the rest of the body. The stability of the shoulder blade comes from the muscles that surround it. These “Scapular Stabilizers” pull the boney plate in different directions and lock it down thus allowing it to remain stationary while the prime movers of the arm (Deltoid, Biceps, and Triceps) use it as their anchor.

Posterior (Back) Shoulder Bony Anatomy

Posterior (Back) Shoulder Bony Anatomy


Anterior (Front) Shoulder Bony Anatomy

Anterior (Front) Shoulder Bony Anatomy

These Scapular Stabilizers consist of the Trapezius (Upper, Middle, and Lower), Rhomboids (Major and Minor), and Serratus Anterior muscles. Both Rhomboid muscles as well as the Middle Trapezius help to pull the scapula in towards the spine while the Upper Trapezius muscle pulls the scapula up and the Lower Trapezius pull it down and in. The Serratus Anterior opposes muscles by pulling the scapula out and forwards towards the front of the ribs. There are other muscles that attach to the scapula and help to stabilize it but these are the major actors on this stage.

We’re discussing these muscles and their role in shoulder function today because we do not use them correctly. If we were properly stabilizing our shoulder blades they would remain firmly pressed to the back of our ribs but the most common postural pattern in the Western World does not do this. Generally we are slouching forward which rolls our shoulder blades out and forward, around our rib cage. This position puts a lot of mechanical pressure on the joint with the clavicle and causes the Upper Trapezius to bear the weight of the shoulder and arm. Through maintenance of this position the Lower and Middle Traps, the Rhomboids, and the Serratus Anterior all weaken from lack of use and are not able to act upon the scapula as they should. When this happens it is called a “Winging Scapula” because the inner edge of the shoulder blade pops away from the ribs and sticks out like a wing and it means that our scapula cannot provide the stability it needs to. Scapular instability leads to increased risk of injury to the shoulder and arm, specifically the rotator cuff muscles and the Acromioclavicular joint (the joint now under pressure between the scapula and the clavicle).

Winging Scapula

If you have been reading my blog for any amount of time you know that I am all about preventing injuries and reducing the risks we expose ourselves too. So to get out of this problematic position we need to retrain our muscles to hold the shoulder blades in place. There are two fairly simple exercises that can accomplish this. The first we’ve talked about before and I call it the “Pocket Push”. The second is demonstrated very well in the video. The sound is a not great so use some headphones or watch it in a quiet space to hear all the details.

No matter how much some of us might wish for wings to fly, a Winging Scapula is not going to help at all. Tuck in those flat little bones and sit up. It will do your body a world of good.

Thanks for reading,
Dr. Ben


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