The sternoclavicular joint permits motion in the anterior and posterior directions about a longitudinal axis, in the cranial and caudal directions about a sagittal axis, and in rotation about a coronal axis. These movements are slightly enhanced and transmitted by the acromioclavicular joint to the scapula. Additional motions of the shoulder girdle described here are those of the scapula.
The scapula connects with the humerus at the gleno-humeral joint and with the clavicle at the acromioclav-icular joint.
With the upper back in good alignment, the scapulae lie against the thorax approximately between the levels of the second and seventh ribs. In addition, the medial borders are essentially parallel and approximately 4 inches apart.
Muscles that attach the scapula to the thorax anteriorly and to the vertebral column posteriorly provide support and motion. They are obliquely oriented so that their directions of pull can produce rotatory as well as linear motions of the bone. As a result, the movements ascribed to the scapula do not occur individually as pure movements. Because the contour of the thorax is rounded, some degree of rotation or tilt of the scapula
Depression accompanies abduction and adduction and, to a lesser extent, elevation and depression.
Although no pure linear movements occur, seven basic movements of the scapula are described:
1. Adduction: Gliding movement in which the scapula moves toward the vertebral column.
2. Abduction: Gliding movement in which the scapula moves away from the vertebral column and, following the contour of the thorax, assumes a posterolat-eral position in full abduction.
3. Lateral or upward rotation: Movement about a sagittal axis in which the inferior angle moves laterally and the glenoid cavity moves cranially.
4. Medial or downward rotation: Movement about a sagittal axis in which the inferior angle moves medially and the glenoid cavity moves caudally.
5. Anterior tilt: Movement about a coronal axis in which the coracoid process moves in an anterior and caudal direction while the inferior angle moves in a posterior and cranial direction. The coracoid process may be said to be depressed anteriorly. This movement is associated with elevation.
6. Elevation: Gliding movement in which the scapula moves cranially, as in "shrugging" the shoulder.
7. Depression: A gliding movement in which the scapula moves caudally. This movement is the reverse of both elevation and anterior tilt
Movements of the Scapula
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