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 gleno-humeral joint is made up of the ball of the humerus and the socket of the shoulder blade which is called the glenoid surface. The top of the arm bone, the humeral head, is large and carries many of the tendon insertions for the stability and movement of the shoulder. The socket or glenoid is a relatively small and shallow socket for the large ball but is deepened slightly by a fibrocartilage rim called the glenoid labrum. Above the shoulder is the acromio-clavicular joint, a joint between the outer end of the collar bone and part of the shoulder blade, a stabilizing strut for arm movement.
The glenohumeral and scapulothoracic joints of the upper limb are acted on by large, strong, prime mover muscles as well as smaller stabilizers. The major back and hip muscles keep the shoulder stable to allow strong movements, the thoracic stabilizers keep the scapula stable so that the rotator cuff can act on a stable humeral head. The deltoid can then perform shoulder movements on the background of a solid base and allow precise placement and control of the arm for hand function to be optimal.
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.
As a person ages, the rotator cuff develops degenerative changes in its tendinous structures, causing small tears in the tendons which can enlarge until there is no continuity between the muscles and their attachments. This leads to loss of normal shoulder movement and can be very painful but is not always so and “Grey hair equals cuff tear” is a common saying. Physios work at rotator cuff strengthening, whilst in massive tears the main shoulder muscles can be progressively strengthened to improve function. Surgery is possible for massive, moderate and small rotator cuff tears and physiotherapists manage the post-operative 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, mobilization 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.
Many other shoulder conditions are managed by physiotherapists, such as hyper-mobility, dislocations and fractures, impingement and tendinitis. Physios manage shoulder hyper-mobility by patient education and stability training and abnormal muscle activity by teaching correct patterns by repetition and biofeedback. Physiotherapy for impingement involves rotator cuff strengthening, sub-acromial injection or surgical management by acromioplasty and tendinitis by local treatment and strengthening. Dislocations and fractures are managed according to the type and severity of injury and according to the trauma surgical and physiotherapy protocols.