By Dr Dan Laptoiu, MD, Bucharest, Romania
Anatomy of the shoulder
The shoulder as seen is constituted of 3 articulations: glenohumeral, acromioclavicular, costoscapular. The glenohumeral joint, being the articulation with most degrees of movement, is inherently unstable. In contrast to the hip it does not have bony support. The glenoid cavity is shallow and normally is in contact with one-third of the articular surface of the humerus in the various positions which occur during the movement of the joint. The glenoid labrum slightly increases the depth of the glenoid cavity but is not responsible for stability which is dependent mainly on the ligaments, capsule, the muscles and tendons which surround the joint, added to the negative intra-articular atmospheric pressure.
The ligaments and capsule are the passive and the muscles are the dynamic stabilising structures.
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