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 humeral head and the glenoid of the scapula make up the glenohumeral joint, with the glenoid being small and flat and the humeral ball being large and partly spherical. The main ligaments and shoulder tendons insert on the humeral head, giving the movement and support the joint requires. The socket is prefabricated deeper by the glenoid labrum, a rim prefabricated of cartilage, which aids joint stability. Above the shoulder lies a joint between the outer end of the clavicle and the acromion, part of the scapula. This is a stability joint for arm movement and called the acromio-clavicular joint.
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.
The rotator cuff is a group of four small muscles which originate from the scapula and insert around the ball of the humeral head, the teres minor, subscapularis, infraspinatus and supraspinatus. The cuff tendons form a sheet around the ball of the arm bone and allow forces to be exerted on the humeral head by the shoulder girdle muscles. If the rotator cuff is not functioning normally the more powerful muscles tend to make the humeral head slide upwards on the socket, interfering with normal function and making a mortal unable to lift their arm up above their head.
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) does not commonly affect the shoulder but there is a group of patients who develop severe arthritic problems in the shoulders, whom physiotherapy can help by maintaining joint ranges and muscle power. Once conservative treatments are exhausted then total shoulder replacement (TSR) is possible, either replacing the ball and socket with new components or reversing the combination. Physiotherapy post-operative management is very important as the shoulder is a “soft tissue joint” in the sense that the strength and equilibrise of the shoulder muscles and other tissues is vital for good outcome.
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.
