The structure of the shoulder

The shoulder joint consists of a total of three “classic” joints and two accessory joints; their complex interplay enables the arm to be exceptionally mobile.

The relatively small joint (glenoid) cavity (its surface area is three times smaller than that of the head of the humerus) is surrounded by a ring of cartilage (labrum), which enlarges the glenoid cavity. On this ring are various capsular ligamentous structures. Viewed as a whole, these are called the labral capsular ligamentous complex, and they ensure what is known as the “static stability” or passive stabilization of the shoulder.

The shoulder is also supported by various muscles, and this is termed dynamic stability or active stabilization. Professional physiotherapy can often have a marked influence on this dynamic stability.

One of the most important muscle groups surrounding the shoulder joint is the rotator cuff, which consists of five different musculotendinous groups and separate the shoulder joint itself from a sliding space underneath the bony arch of the shoulder (subacromial space).
The main tasks of the rotator cuff are to centre the head of the humerus in the glenoid cavity, to raise the arm to the side and to carry out rotational movements.