Understanding the shoulder joint and the rotator cuff - an osteopathexplains

The function of the shoulder joint is reflected in its unique structure in much the same way as the hip joint and as the founder of osteopathy Andrew Tailor Still believed, once the anatomy is understood, the osteopath can figure out the pathophysiology.

Let us consider the function of the shoulder joint. It is to guide the upper limb through space in order that we can use the hand to perform our daily activities. Circumduction of the shoulder joint allows a massive range of movement, much more so than the hip is capable of achieving. The hip's strong ligaments and tight capsule play a crucial role in stabilizing the joint but it is primarily the bone which limits hip movement. The deep acetabulaum provides a snug home for the femoral head stabilized by the congruence of the two articular surface. The end result is a tight-fitting stable joint whose range of movement increases only as a result of features unique to the hip that have evolved with time such as the femoral neck and various angles of anteversion to improve the range of movement.


The stability of the shoulder however is compromised for the sake of mobility. Unlike the femoral head which can remain attached to the acetabulum even after ligaments and muscles have been removed, the humerus which lacks congruence with the shallow glenoid cavity would fall away completely if not for the muscles, ligaments and capsule surrounding it.


What the glenohumeral joint lacks in bony congruity it makes up for in a complex arrangement of muscles which act as joint movers and tensile ligaments to provide added support. Furthermore, stability of the gleno-humeral joint is reenforced by no-less than 4 other joints: the scapulothoracic joint, the acromioclavicular joint, the acromioclavicular joint and the sternoclavicular joint.


The muscles that control movement of the shoulder can be divided into 2 groups, much the same way as the hip; long muscles and short muscles. The long muscles such as biceps brachii, coracobrachialis, deltoid as well as secondary muscles like triceps, pectoralis major, teres major, latissimus dorsi and trapezius. The short muscles are supraspinatus, infraspinatus, teres minor and subscapularis and are commonly referred to as the rotator cuff. Whilst working together synergistically these two groups of muscles have a different role in controlling the movement of the glenohumeral joint and any dysfunction in one group is likely to be reflected in problems in the second group.

The long group of muscles have the role of moving the shoulder joint since they have a greater mechanical advantage over a larger range of movement. Due to the glenohumeral joint's lack of congruity the axis of movement is constantly changing as it slides around the glenoid fossa. Therefore the short muscles have the job of finely controlling the movement of the head of the humerus as it ducks underneath the coracoacromial joint. They have the job of orienting the head of the humerus for the movement of the humerus and so the short muscles, the rotator cuff muscles, can be defined as the “fixers” whilst the long muscles can be defined as the “movers”. The supraspinatus muscle pulls the head into the glenoid and slightly rotates the humerus into abduction. The infaspinatus muscle rotates and slightly pulls it down,. The teres minor muscle pulls the head of the humerus down in a slightly different direction and the subscapularis muscle pulls the head into the glenoid but it is has mainly a rotatory action, internally rotating the humerus along its longitudinal action.
Having explained the unique structure of the glenohumeral joint and its dependence on muscluar support the osteopath can start to understand the unique pathophysiology of the joint. Unlike the hip which suffers mainly from osteoarthritis, the shoulder is prone to soft-tissue injuries; capsulitis (frozen shoulder), tendonitis, rotator cuff tears, bursitis and shoulder dislocation. The osteopath therefore needs to put a strong emphasis on understanding the patient's unique way of using the shoulder joint and how the day to day use may be disturbing the fine balance between the long and short muscles. First the osteopath must decide what may be disturbing the fine movement of the rotatotor cuff thus causing friction, compression or ischemia of the surrounding soft tissues and then it is the osteopath's job to try to reintegrate the structures of the shoulder joint using careful osteopathic techniques and a fine osteopathic hand.

Video: Combined techniques for the shoulder

For more information on shoulder problems and sports injuries: http://www.osteopath.co.il/sports-injuries.php

For more information on shoulder prolems in Hebrew: http://www.osteopath.co.il/sports-injuries-heb.php