Yoga Anatomy: Reducing Shoulder Impingement

Our wonderful shoulders are the most mobile joints in the body and, for anyone who has done any amount of Hatha Yoga flow, we can appreciate how much the shoulders are engaged and challenged in our practices.  Given how frequently we load and stress the shoulders in yoga, it is ideal to move the shoulders with intelligence, mindfulness, and attentive care. One aspect of mindful movement and engagement is reducing the onset of shoulder impingement.

Our shoulder joints are made from a ‘ball and socket’ design. The upper arm bone (humerus) has defined structures at its proximal end (closest point to the center of the body).  At the proximal end of the shaft, we see that the humerus has boney processes (called tubercles where tendons attach). Moving towards the shoulder joint, the humerus has a neck that transitions into a ‘head’ or the ball portion of the joint.  The humeral head inserts into the socket (glenoid fossa or cavity) forming this highly moveable joint.  The socket is part of the shoulder blade (scapula bone).  There is another part of the shoulder blade with a boney projection called the acromion process which is positioned above the humerus. You call feel the acromion process on yourself by taking one hand over and to the back of the shoulder blade. Run your fingers along the shoulder blade to find a horizontal line of bone – this the spine of the scapula. Run your fingers all the way to the end into your shoulder  – where this ends is your acromion process.

Between the acromion process and the tubercle region of the humerus is the ‘subacromial space.’ This is where our attention goes regarding shoulder impingement considerations. Deep above the spine of the scapula runs one of your rotator cuff muscles (supraspinatus muscle), which has its tendon traveling through the subacromial space and attaching onto the greater tubercle of the humerus. To offer some protection to this tendon, there is a small sac of fluid (bursa sac) between the tendon and the acromion process.

When we stand in Mountain pose (arms relaxed), there is ample space in the subacromial space for the supraspinatus tendon and the bursa sac. When we lift our upper arm bone outwards (abduction) or towards certain angles of significant forward movement (flexion), the humerus closes into the subacromial space. For some people, due to bone structure and reduced subacromial space, they are more prone to having the tendon and/or bursa sac being compressed and stressed (aka shoulder impingement). With frequent compression, the tendon and/or bursa sac may develop conditions of inflammation. As with any acute or chronic development of shoulder impingement conditions, you will want to consult a qualified health professional for proper assessment and therapeutic treatment.

Knowing the potential for shoulder impingement, we can apply a couple of movement techniques to retain more subacromial space and reduce compression and stress going into the tendon and bursa sac.

External Rotation

The first movement application is external rotation of the humerus, when you abduct and/or deeply flex the shoulder joint. When the upper arm bone internally rotates during abduction and/or flexion, the greater tubercle moves more closely into the subacromial space thus increasing the potential for impingement. When we externally rotate the upper arm bone, it shifts this boney process somewhat away leaving more space for the supraspinatus tendon and bursa sac.

Upwards Rotation

The second movement we can employ is scapular upwards rotation. The shoulder blade can be taken through 6 movements – one of them is an upwards rotation. When we significantly abduct or flex the shoulder joint, we want the shoulder blade to move with the upper arm bone (this is called scapulohumeral rhythm). Besides sustaining more fluid joint congruency and connection during these arm movements, maintaining this joint rhythm reduces the onset of shoulder impingement. Upwards rotation of the scapula is similar to a spinning movement of the shoulder blades away from the spine causing the socket and acromion process (all connected as one bone) to tilt upwards. The upwards lift of the acromion retains space in the subacromial space as the arm bone lifts through abduction or flexion.

When we combine external rotation of the shoulder with upwards scapular abduction, this becomes a movement of integrity and beauty for the shoulder joint – retaining space while enhancing stability. Consider all the yoga postures and transitions where you can take advantage of this movement combination: sun salutation arm circles; downward facing dog; tree pose; crescent lunge/warrior 1; half moon; and other reaching side bends.

Play with these movements in the shoulder and shoulder girdle. Keep in mind that bone structure can be highly variable, therefore some people benefit more from these movement applications than others. Also examine with these movements how the rest of the body (and kinetic chain of other joints involved like the elbow and wrist) is affected. Rarely in yoga are movements tightly isolated in one joint region. As you find your way into postures, maintain ease and playfulness (versus rigidity) as this will greatly increase your capacity to explore these techniques towards spaciousness and integrity.