The function of the human arm is to allow placement of the hand in useful positions so the hands can perform activities where the eyes can see them. Because of the huge range of positions required the shoulder is very flexible with a large motion range, but this is at the expense of some reduced strength and greatly reduced stability. A “soft tissue joint” is often a description of the shoulder, indicating it is the tendons, muscles and ligaments which are important to the joint’s function. Shoulder treatment and rehabilitation is a core physiotherapy skill.
The shoulder joint is constructed from the socket of the scapula and the humeral head, the ball at the top of the upper arm bone. The head of the upper arm is a large ball and important tendons insert onto it to move and stabilise the shoulder, but the shoulder socket, the glenoid, is small in comparison and very shallow. A cartilage rim, the labrum of the glenoid, deepens the socket and adds to stability. The acromio-clavicular joint lies above the shoulder joint proper and provides dynamic stability during arm movements, being made up from part of the scapula and the outer end of the clavicle.
The major stability and flexibility joints of the upper limb shoulder girdle are the scapulothoracic and glenohumeral joints and these joints are held steady and moved by large and powerful muscles. The pectoralis major and latissimus dorsi muscles stabilise and perform strong movements, the serratus anterior stabilises the scapula on the thorax, the rotator cuff stabilises the humeral head on the socket and the deltoid and other muscles perform movements. The shoulder blade and thorax need to be kept in a stable relationship for the glenohumeral joint to perform precise and controlled movements.
Around the shoulder all the muscles narrow down into flat, fibrous tendons, some larger and stronger, some thinner and weaker. All these tendons are anchoring themselves to the humeral head, allowing their muscles to act on the shoulder. The rotator cuff includes a group of relatively small shoulder muscles, the subscapularis, the supraspinatus, the infraspinatus and the teres minor. The tendons form a wide sheet over the ball, allowing muscle forces to act on it. The rotator cuff, despite its name, acts to hold the humeral head down on the socket and allow the more powerful muscles to perform shoulder movements.
With age, small degenerative tears occur in the tendons of the cuff, in some cases painful and in others not, causing loss of movement and strength. As tears progress they can become massive, cutting off the cuff muscle power from the humeral head and severely reducing function. Rotator cuff strengthening work is performed by physiotherapists and if the tears are severe they concentrate on anterior deltoid strength to improve functional ability in the absence of cuff power. Shoulder surgeons can repair many rotator cuff tears and physiotherapists rehabilitate patients following the shoulder protocols.
Osteoarthritis (OA) more commonly affects the hips and the knees, however the shoulder can be severely affected in which cases physiotherapy can help with advice, mobilisation of the joints and work on strength and joint motion. Once physiotherapy treatment has been tried then total shoulder replacement is the only remaining treatment option, surgical replacement occurring of the head of the arm bone and the socket of the shoulder blade. As the shoulder is referred to as a “soft-tissue joint” it is the balance and strength of the tendons, muscles and ligaments that determines a good outcome for the replacement. Physiotherapists closely follow the surgical protocols to get the optimal results.
Physiotherapists treat many other types of shoulder problems such as impingement, tendinitis, hypermobility, abnormal muscle patterning, fractures and dislocations. Impingement is treated by strengthening the rotator cuff or by subacromial injection or acromioplasty operation, where the end of the acromion can be excised. Tendinitis is treated by direct treatment of the tendon and graded strengthening and hypermobility by stability work and accepting the limitations dictated by the condition. Abnormal muscle patterning is managed by teaching normal patterns functionally and fractures and dislocations by the protocols laid down by the surgeons and trauma physiotherapists.