Yoga And The Shoulder Joint
Understanding the structure of the shoulder joint and its various anatomical components can help you to understand how the shoulder joint works, how it can be injured and how to prevent or heal injury with yoga.
The shoulder is actually one of the most complex of all the joints, and having the greatest range of motion of any articulation in the body, it can be susceptible to injury.
In learning and understanding Anatomy and Physiology it is sometimes helpful to look at the body in layers: whilst remembering that the body is a whole and in reality not divided so neatly into convenient little compartments!
At the deepest level of the body are the bones and joints which provide the framework for the body and where movement happens. The bones that make up the shoulder are
- the humerus (arm bone)
- the scapula (shoulder blade)
- the clavicle (collar bone).
- The roof of the shoulder is formed by a part of the scapular called the acromium, a protuberance at the top of the scapular.
There are actually 4 joints that make up the entire shoulder.
- Glenohumeral Joint is considered a ball-and-socket joint which is a bit misleading however as “the ball” doesn’t actually have a clear socket as such. It is formed where the head of the humerus fits into a shallow hollow on the scapular called the glenoid. This is where dislocation of the shoulder occurs, whereby the ball slips out of the socket.
- Acromioclavicular, (AC) Joint, is where the clavicle meets a bony protuberance on the top of the scapular called the acromium.
- Sternoclavicular, (SC) Joint is where the clavicle meets the sternum (breastbone), and thereby connecting the arms and shoulders to the main skeleton.
- Scapulothoracic Joint is actually a false joint where the shoulder blade glides over the back of the ribcage. Although not a real joint, it is a very important area as muscles surrounding the shoulder blade have to work together to keep the socket properly aligned during shoulder movement.
All of these joints interact to create the various movements that we see and feel in the shoulder joint.
There are several important ligaments in the shoulder which can be seen in the image below. Ligaments are soft tissue structures that connect bones to bones, stabilizing the joint whilst allowing movement. The joint capsule is a water tight sack that surrounds the joint and in the shoulder, the capsule is formed by a group of ligaments that attach the humerus to the glenoid.
Muscles and Tendons
Tendons are made of a tougher material than ligaments and are like tight ropes that connect muscles to bones. When a muscle contracts, it pulls on the tendon which then pulls on the bone, causing movement.
Four tendons connect the deepest layer of muscles that hold the shoulder joint together, known collectively as the rotator cuff. These muscles help to lift the arm and to rotate the shoulder in different directions. Just before these muscles attach to the upper end of the humerus they join to form a single tendon, also called the rotator cuff.
The Rotator Cuff Muscles
- Supraspinatus is the most commonly injured muscle in the shoulder. If you place your fingers in the groove at the top of your shoulder blade and abduct your arm out to the side, you will feel this muscle contract. This muscle abducts the Glenohumeral Joint and stabilizes the head of the humerus in the glenoid cavity.
- Infraspinatus is the second most commonly injured muscle to the shoulder joint. If you place your hand lower down on your scapula and externally rotate your shoulder you will feel the fibres contracting. This muscle adducts and extends and externally rotates the Glenohumeral Joint.
3. Subscapularis lies on the inside of the scapula and so is not so easy to feel, but if you lift your arm forward and poke your thumb in the flesh under the arm pit your can access it. You can feel the fibre contracting if you internally rotate your shoulder. Subscapularis internally rotates the glenohumeral Joint and together with the other rotator cuff muscles, helps to stabilize the head of the humerus in the glenoid cavity.
4. Teres Minor is a slim, narrow muscle which is involved in the external rotation of the shoulder joint. It can be felt by reaching under your arm pit and feeling the outside border of your shoulder blade. Place your fingers on the upper third of this border and then rotate your shoulder outwards and you should feel a small muscle bulking up.
These deeper muscles are layered over by larger, stronger muscles that attach directly to the acromion process. The muscles of the rotator cuff guide the actions of the arm bone itself, while other larger muscles control the actions of the shoulder as a whole, with both the arm bone and the shoulder blade functioning as one unit.
The outer layer of the shoulder muscle is formed by the deltoid, which is the largest and strongest muscle in the shoulder. This triangle shaped muscle provides the power to lift the arm once it is away from the body. The muscle fibres can be divided into three segments: the anterior, middle and posterior fibres. All three groups abduct the arm but the anterior and posterior fibres are antagonists, meaning they have opposite actions.
The anterior fibres flex and internally rotate the shoulder whereas the posterior fibres extend and externally rotate the shoulder. You can feel this muscle very easily by cupping your hand over the outside of the shoulder and moving your arm out to the side, forwards and backwards; you will feel the fibre contracting.
Raising the arm up to 60- 80° is actually the responsibility of the deltoid muscle. Then the rotator cuff and especially the supraspinatus muscle take over and raise the arm to about 100°-120°, after which the deltoid takes over again all the way to 180°.
One of the most common causes of shoulder pain is an injury to the supraspinatus muscle. This can be caused by an accident, such as falling on the affected arm, but many times it is simply through overuse or in the case of yoga, repetitive action with faulty alignment. The pain can affect your mobility to such a degree that you can have difficulty lifting the arm to get dressed or comb your hair. Some people may also feel a clicking or catching when they move their shoulder.
Triangular Forearm Support
I am repeatedly marvelled at the wisdom of the ancient yogis, to heal the body without MRI scans and sophisticated surgery. This simple exercise below, actually trains the subscapularis, (the muscle below the shoulder blade), to take over the job of the injured supraspinatus. Holding for just 30 seconds can give immediate pain relief and practicing a few times a week for 2 to 3 weeks can completely heal rotator cuff injuries.
- Interlock your hands and make an equilateral triangle with the forearms against a wall.
- Place the top of your head in the centre of the triangle.
- Walk away from wall so the torso is slanted toward wall and some weight is now on your head.
- Draw your shoulder blades back, down and apart, still pressing shoulders away from the ears with the forearms against the wall.
- Hold position for 30 seconds.
- Come away from wall, stand up straight.
- Stand up and boldly raise arms straight up.
If you suffer from rotator cuff problems, I recommend you try this practice. It is important when you raise your arms up at the end, to do so confidently and not stop at 90° waiting for it to hurt like it normally does. A high percentage of people experience immediate relief and if this is the case for you, then practicing 2 or 3 times a week for several weeks could well bring a complete recovery.