The shoulder is the most commonly discussed joint in the body when pertaining to yoga, yoga instructors, and the likes of the fitness world.

It is also known as one of the most commonly injured and at-risk joints in the body, mainly due to the anatomical structure and mechanics of the joint.

Sometimes it’s even referred to as the most unstable joint in the body—however, I disagree. Unless trauma, repetitive overuse, or scapular dyskinesis are involved, the shoulder remains fairly stable due to the supporting structures in and around the joint capsule if functioning correctly.

 All about scapular dyskinesis

Scapular dyskinesis, in layman’s terms, means an imbalance affecting the normal position and motion of the shoulder blade as it pertains to its combined movement with the shoulder joint.

This may occur during overhead reaching, such as in Downward-Facing Dog and Chair pose, as well as when reaching out to the sides and in front, such as in Extended Hand to Big Toe.

The marriage between the scapula (shoulder blade) and humerus (arm bone), during shoulder movement, has not received much mainstream attention in the yoga world.

As a practicing physical therapy clinician and yoga instructor, I believe working toward proper scapular humeral rhythm is crucial.

To ensure shoulder safety and stability, you have to understand the correct anatomical and biomechanical movement of the shoulder joint while teaching or practicing yoga.

How the shoulder moves

Glenohumeral joint

(glen-oh-hue-mer-al)

Known to be a shallow semi-ball and socket joint, the glenohumeral joint is held in place by a thick cartilaginous labrum that acts to suction cup the head of the humerus into the socket and keep it from falling off. The supporting structures surrounding the joint are layers of muscular tissue that stabilize and create movement at the joint.

Acromioclavicular joint

(acro-mio-clav-ic-u-lar)

This is where the clavicle (collarbone) attaches to the shoulder blade. To find the acromioclavicular joint (AC), trace your collarbone from your sternum to the tip of your shoulder.

This is a common area of impingement and tendonitis, mainly from incorrect positioning of the shoulder during repetitive movement. It can also be due to a downward sloping acromion that rubs on soft connective tissues. This creates irritation, inflammation, and eventually leads to fraying of the tissues and tearing. That’s a nama’NOT GOOD!

Sternocalvicular joint

(ster-no-clav-ic-u-la­r)

This is the only true attachment of your arm to the trunk. Where your collarbone meets your sternum is where you can find the sternoclavicular joint (SC). Imagine this joint as a 4-way joystick with three degrees of movement:

•  1) Elevation and depression. this movement refers to the upward and downward rotation of the shoulders. To feel this, place your hand on the SC joint and shrug your shoulder up and down. You will feel the collarbone moving up and down at the joint level.
•  2) Protraction and retraction. When your shoulder blades are apart, they are protracted. When they are together, they are retracted. To feel this, place your hand on the SC joint and press your shoulders forward as if to collapse the chest and feel the clavicle tilt forward. Draw your shoulder blades together as if pressing them into each other and you will feel the clavicle tilt backward.
•  3) Axial rotation. This movement refers to the arm as it is lifted overhead; the collarbone then rotates passively as the scapula rotates upward. To feel this, place your right hand on the left SC joint, lift the left arm overhead, and then lower it back down. You will feel the clavicle roll backward and gradually return to neutral position while lowering the arm.

Scapulothoracic joint

(scap-u-loh-thor-as-ic)

This is not a true anatomical joint as it is void of typical characteristics, such as fibrous, cartilaginous connection or synovial fluid. The scapulothoracic joint is a connection (articulation) of the scapula with the ribcage (thorax). It is dependent upon the joint integrity and movement quality of the AC joint and SC joint.

Any movement of the shoulder blade along the back requires movement at the AC joint, SC joint, or both. This allows for the functionality and congruency associated with movements of the arms.

Stability and balance

 If you move your shoulders around, lift them up, set them down, or push them forward and back, it is easy to understand how all four of these joints must work simultaneously together. Dysfunction or dyskinesis can be detrimental and all but kill your practice as well as your joints.

It’s imperative that we continue to deepen our knowledge of not just the structure of our shoulders, but the importance of developing a practice that is focused on stability and balanced movement in relation to the health of our joints and body.

Stay tuned for the second installment of Yoga and Shoulders: It’s a Scapular Matter, where we will discuss the injuries that can occur, due to muscular imbalances built through incorrect shoulder mechanics in your yoga practice.

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