The gleno-humeral joint, known in lay terms as the shoulder, is a vital part of the links in the upper limb and responsible for our ability to place our hands where we can see them to perform activities. Because flexibility is a prime requirement the shoulder is a less stable joint with moderate muscle power and a large range of motion. It is described as a "soft tissue joint", implying that the joint's functional ability is dependent on its soft and not its hard components. Physiotherapists are closely involved in treating and rehabilitating the shoulder, dealing with the muscles, ligaments and tendons.
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 glenohumeral and scapulothoracic joints of the upper limb are acted on by large, strong, prime mover muscles as well as smaller stabilisers. The major back and hip muscles keep the shoulder stable to allow strong movements, the thoracic stabilisers 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.
The shoulder muscle tendons become flatter and thinner as they approach and then insert themselves onto the head of the humerus. By this way the rotator cuff, a group of four muscles including the supraspinatus, infraspinatus, teres minor and subscapularis, is able to exert its forces on the humeral head. The tendons coalesce as they surround and insert onto the ball of the humerus, forming a cuff around the ball, centering the ball on the socket to counter the tendency to slide upwards under muscle activity. Keeping the ball centred on the socket means the larger and more powerful muscles can perform functional shoulder and arm 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.
The shoulder joint is not typically affected by OA (osteoarthritis) but when it is physiotherapists treat arthritic shoulders by joint mobilisations, muscle strengthening and ranges of motion. Once physio has nothing else to offer, total shoulder replacement is one of the further options, with various surgical techniques involving replacing the humeral ball and the scapular socket either anatomically or in reverse. The shoulder is often called a "soft-tissue joint" as the soft tissues, their strength and balance, are vital to the function of the joint. Post-operative physio management is essential as the correct protocol must be closely followed to ensure success.
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.
