The scapula is all important in shoulder movement. Any force generated by the shoulder requires the scapula to remain stable, forming a platform against which the shoulder can operate in a pushing or pulling motion. Much like the floor acts as a platform against which you jump when you launch yourself upward. There is an inherent relationship between the scapula and movement of the humerus {arm} which increases the effectiveness of the available 'range of motion'. Each moves in cohesion with the other to provide the most stable and efficient movement of this complex joint.+
Like a swivelling seat for a gunnery shooter, the scapular must move to provide a base or platform of movement for the arm. This means that wherever the arm moves to, the scapula must move correspondingly to enable a platform or base against which to push. As the arm (humerus) is able to move so widely in such a wide arc of motion, the scapula must be able to move and rotate in a corresponding fashion providing adequate support and enabling efficient, functional biodynamics. In this way the scapula must be able to move upward (elevation), downward (depression), medially (protraction) laterally (retraction) as well as tipping internally and externally on its own axis according to where best the support must come from.
This is where so much of the shoulder function is reliant on the big power muscles of the back. The rotator cuff is often cited as the primary 'demon' in shoulder pain. This may be due to the regular occurences of impingement of the supraspinatus tendon as described in our earlier article. However the rotator cuff is dependent upon the scapular stabilisers to provide support and the foundation of shoulder movement. There are over 20 muscles that connect to and act on the scapula providing it with support and movement. The primary muscles of support are the Rhomboids, the Serratus Anterior and the Trapezius. Latissimus Dorsi, Levator Scapulae and the Rotator Cuff itself also have a large role to play in keeping the scapula in place and ensuring good 'glenohumeral rhythm' (co-ordination of arm and shoulder).
Movements that effect these muscles can upset the ability for the scapula to remain solid and thus adhesions, strains, trigger points from overloading and overdevelopment of any one of these muscles has an important role to play in ensuring good shoulder function. These muscles connect to other various parts of the body and thus are subject to injuries in different locations. An injury in the ribs may effect how the serratus anterior moves and thus how effective the shoulder can move. The same with an injury to the thoracolumbar fascia in the back into which the latissimus dorsi inserts. When you understand these relationships, you start to get an idea of how much can effect shoulder function.
If the scapula is not held in place against the rib cage wall, the arm is operating on an unstable platform. Essentially, much of it's energy is being lost without a stable platform. Like a push up on a bosu ball, you have to exert more energy to maintain control. This is exactly where an unstable scapula can result in shoulder pain as movers of the arm and shoulder become overloaded due to an unstable base. In this way, scapula stablisation is the primary concern for rehabilitating shoulder function - not the injury, but the function. You want to get back to being able to swing your arm after injury? Rehabilitate the injury but make sure you have a strong platform established = otherwise the injury will return with vigour.
When talking about stabilisation we must also consider how this effects power. For those involved in heavy lifting, power lifting, CrossFit etc, you must consider how stable is the base against which you are working. A catapult can only fire effectively from a base that is stable - if the base is unstable, then much of the power generated by the swing is lost in the physics of motion as force is dissipated through instability. A catapult on a wobbly platform won't throw as far. Just so - a lift or powerful all out thrust, will lose force if the base is not stable. Thus any power lifting requires the stability of a joint to be maintained to exert maximum force.
When we talk about scapula stabilisers, we must also consider those muscles that act on the arm as well. Much of this comes into play with the anterior muscles of arm and shoulder and primarily constant overdevelopment or shortening of these muscles. Pectoralis, subscapularis, biceps brachii are all involved in the 'pushing motion' that is often overdeveloped in avid gym goers and resistance trainers. One of the most common things I deal with is the failure to balance this with the powerful scapula retractors that perform the opposing force at the back, pulling the scapula back against the rib cage and keeping it in it's position. With overdevelopment of the anterior (or glamour muscles if you will) you can imagine how the scapula starts to be pulled forward or 'protracted'.
Any muscle, sensing too much length, will trigger a response in the nerve cells (golgi tendon organs) which triggers the brain to initiate the muscle to contract back to it's 'established length'. However if skeletal alignment is placing tensile strain on a muscle, it contracts continuously but in vain. This causes adhesions and tightening as the muscle is under tensile strain. When these adhesions become too numerous and the fascial layer becomes taut through over-extension, a smaller movement may trigger injury. Such as in picking up the grocery bag. Sound familiar? Hence overloading muscles that act in cohesion with other muscles can increase the liklihood of injury. They create uneven tension and or contraction of muscles against the pull of strain.
Whenever a muscle is over-used and begins to fail, trigger points often form and this leads to compromised function of muscles further down the chain. Where a muscle that is active in a highly co-ordinated action is compromised, the whole action becomes compromised. The body will find ways to enable to movement, but in so doing will overload other muscles to enable it. This is fine short term, but after long term exposure to increased workload, any muscle will ultimately fail, shorten or tear under the load.
Ensuring all these muscles and primary stabilisers are in good condition and functioning optimally is one of the primary advocates for soft tissue therapy and regular massage treatments. Ensuring that efficient function is also maintained further down the chain in the muscles of the hand, arm, mid back and neck is also of primary concern to ensuring joint integrity and a healthy shoulder. When the joint is compromised, it is rarely a case of treating only one aspect of this complicated joint. Due to the nature of movement in a shoulder, re-educating the body to operate efficiently is a slow process. As M.Meyer states, "Re-education of stabilising muscles is not merely a question of strength, but one of control. It takes time, concentration and effort to re-educate the body to use these small muscles again."
+For more on this relationship and scapulohumeral rhythm click here
^see previous article on 'Shoulder Impingement'
++ other muscles contributing include pectoralis minor and subclavius via the corocoid process in the anterior chest
