Shoulder injuries are very common in contact sports, but can also result from overuse, particularly in racket sports. Very often the rotator cuff muscles which support the shoulder-joint are injured. However, as important as rotator cuff rehabilitation is in treating the injured shoulder, the functional ability of the scapula (shoulder blade) and its attaching muscles must not be neglected nor should the functioning of the rest of the body.
There are four rotator cuff muscles and they run between the scapula and the head of the humerus (upper arm), they are responsible for stabilising the joint between the humerus and the scapula (gleno-humeral joint or GHJ) when we move our arms. However, correct functioning of the shoulder complex consists of more than just active GHJ stability. These are other elements are:
– Scapula mobility
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– Scapula stability
– Thoracic extension
For our shoulders to function correctly, the scapula must be able to move unrestricted through its full range of movement, passing around the posterior-lateral thoracic wall, known as the Scapulo-Thoracic Joint (STJ). However, no actual bony articulation exists between the scapular and thoracic wall.
This means that as the arm moves from the shoulder in any direction, a significant amount of the movement needs to come from the STJ. This relationship between shoulder blade motion and upper arm motion is known as Scapula-Humeral Rhythm. As this name suggests, the scapula and humerus need to move in harmony to get our shoulders moving optimally.
The important purposes of scapula-humeral rhythm are:
1) To maintain the length-tension ratios in the rotator cuff muscles as the shoulder moves through range – maintaining their stabilising properties at the GHJ.
2) To reduce relative motion local to the GHJ. If shoulder motion occurred purely from the GHJ with a fixed scapula, the head of the humerus would impinge on the surrounding bony structures leading to injury to for example, the rotator cuff tendons.
The scapula functions as a stable, yet mobile base, for the upper arm to articulate on. The GHJ dictates that it must, through its muscular attachments, posses the mobility to work through sufficient range at the STJ, while at the same time controlling motion to ensure a stable base for all arm activity. All the muscles of the scapula therefore need work in synergy.
For the STJ to be able to function properly through its full range of movement, there must be sufficient thoracic (upper) spine motion in all directions, especially into extension (movement away from the body). It should also be noted that adequate motion at the sterno-clavicular joint (SCJ) and acromioclavicular joint (ACJ) must also be present to optimise the function of the shoulder complex.
– Restricted/altered scapular motion
As previously discussed, for the shoulder complex to move through its normal ranges of motion much of the movement has to come from the scapular. If scapular movement around the thoracic wall is altered – either through soft tissue restriction, inhibition of the scapular stabilising muscles or lack of thoracic spine extension, an increased amount of the shoulder’s range of movement will have to come from the GHJ.
Restricted shoulder movement will in all likelihood result in shoulder impingement.
– Winging/tipping of the scapular
Winging is a common dysfunction where the entire medial border of the scapular (the edge of the scapular closest to the spine) visibly lifts off the thoracic wall. This winging is caused by the inability of the scapular stabilising muscles to fulfil their role of controlling scapular motion.
Tipping is similar in that there is a prominent lifting off the thoracic wall, but this time it is present in a slightly different location – the inferior-medial border.
This indicates both weakness in the lower scapular stabilisers and potentially tightness in the anterior (front) structures, such as the pectoralis minor (chest muscle). Tipping will also lead to a restricted shoulder movement and therefore an increase in the likelihood of developing shoulder movement issues around the GHJ.
The function of the shoulder girdle dictates that the rehabilitation of a shoulder injury needs to focus on the balance between mobility and stability. Failure to do so could result in compromised recovery.
Consequentially it is important to see the body as a kinetic chain i.e. with each body part (the links), working harmoniously to create optimum movement (the chain). So although an athlete with an injured shoulder may need to specifically strengthen that structure, the function of the whole kinetic chain must be re-trained.
It is important to ensure that the scapular is functioning correctly as previously discussed, but as rehab progresses, it is also important to retrain the loading of the hips during functional movements, so that the upper body and lower body works together. It’s often the breakdown of the kinetic chain and the subsequent habitual changes in biomechanics that results in shoulder injury.
Therefore, these biomechanical habits need to be corrected during rehabilitation to reduce the risk of re-injury. Remember, although strengthening is vital, if the kinetic chain is moving incorrectly – the same outcome i.e. re-injury is likely.