Movements of the arm
The glenohumeral joint is highly mobile resulting in a wide range of movements of the arm.
Arm flexion
Arm flexion represents rotation in the anatomic plane such that the distal humerus moves ventrally. Is represents raising the arm and isolated flexion can achieve approximately 150-170° of movement.
- deltoid (anterior fibers)
- pectoralis major (clavicular part)
- biceps brachii (long and short heads)
- coracobrachialis
Arm extension
Arm extension represents the opposite movement to arm flexion and can only achieve about 40° of movement in most individuals.
- deltoid (posterior fibers)
- latissimus dorsi
- teres major
Arm abduction
Arm abduction represents movement of the arm away from the midline of the body and, in most cases isolate abduction can be achieved to 160-180°.
- deltoid (middle fibers)
- supraspinatus
Arm adduction
Arm adduction represents movement of the arm towards the midline and most individuals can manage 40° of isolated adduction.
- pectoralis major (sternal part)
- latissimus dorsi
- teres major
- teres minor
Arm internal rotation
Internal (medial) rotation represents the movement of the humerus when an arm flexed to 90° at the elbow is rotated around the longitudinal plane of the humerus such that the hand moves towards the midline of the body. The degree of rotation is dependent on the degree of abduction at the shoulder. In adduction internal rotation can be up to 70°. As the arm is abducted this increases towards 95°.
- subscapularis
- latissimus dorsi
- teres major
- deltoid (anterior fibers)
Arm external rotation
External (lateral) rotation describes external rotation of the humeral around its longitudinal axis. As with medial (internal) rotation, the degree of rotation is dependent on the degree of abduction. When the arm is adducted, medial rotation of 40-55° is possible. However, as the arm is abducted, this increases towards 70°.
- infraspinatus
- teres minor
- deltoid (posterior fibers)
Circumduction
Circumduction is the orderly combination of shoulder flexion, abduction, extension and abduction (or the reverse) to trace a cone with the arm. It is hence produced by co-ordination of all the muscles that produce these individual movements but also relies on other joints of the pectoral girdle such and the acromioclavicular joint and scapulothoracic joint.
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