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Shoulder Joint

• The shoulder serves to connect the upper extremity to the trunk.
• The muscles acting here are often denervated in brachial plexus and proximal peripheral nerve injury patterns.
• With dysfunction at the shoulder, the upper extremity cannot be properly positioned in space to perform normal functions even if normal hand or other distal function is preserved.
• Restoration of shoulder movement must be a priority in peripheral nerve injury patients.
Structures of the Shoulder
• Bones:
• Thorax (including sternum, ribs, spinal vertebrae, etc.)
• Clavicle
• Scapula
• Humerus
• Joints:
• Scapulothoracic
• Acromioclavicular joint
• Glenohumeral joint
• Sternoclavicular
Movements of the Shoulder
Movement at the shoulder is complex:
• The shoulder glenohumeral joint where the key motion occurs is dependent on normal movement at the shoulder girdle (which is made up of the scapula/clavicle and their connection to the thoracic). 
• Dysfunction of scapular motion (which can be seen in various patterns of brachial plexus and peripheral nerve injury) can greatly impede shoulder, and thereby upper extremity, movement.
Key movements:
• Flexion and extension are movements about a coronal axis.
• Abduction and adduction are movements about a sagittal axis.
• Horizontal abduction and horizontal adduction are movements in a transverse plane about a longitudinal axis.
• Internal/Medial rotation and external/lateral rotation are movements about a longitudinal axis through the humerus.
Scapular Movement (in turn allows normal glenohumeral joint movement):
• Abduction and adduction
• Upward (lateral) rotation and downward (medial) rotation
• Anterior tilt and posterior tilt
• Elevation and depression
Glenohumeral Joint Movement:
• Anterior flexion and posterior extension
• Abduction and adduction
• Horizontal abduction and horizontal adduction
• Lateral/external and medial/internal rotation
• Circumduction