MOVEMENTS 

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    There are many movements that occur at the shoulder joint. During all of these movements, the four rotator cuff muscles keep the head of the humerus in the glenoid fossa.

Flexion, Extension and Hyperextension of the shoulder occur in the sagittal plane.

Abduction and Adduction of the shoulder occur in the frontal plane.

Horizontal Abduction and Adduction occur in the horizontal plane.

Internal and External rotation also occur in the horizontal plane.

Circumduction of the shoulder occurs in all planes.

    The shoulder joint is unique in that it also has a special movement called glenohumeral (scapulohumeral) rhythm. This is the movement of the scapula relative to the humerus, when the humerus moves throughout its full range of abduction. This combined movement also occurs in the frontal plane. There are three stages to this "rhythm":

"Setting Phase"--As the humerus moves from 0-30 degrees of abduction, the scapula prepares to move, but does not move.

"1-2 Phase"--As the humerus moves from 30-90 degrees of abduction, the scapula abducts and upwardly rotates 1 degree for every 2 degrees of humeral motion.

"1-1 Phase"--As the humerus abducts from 90 degrees to full abduction (normally 180 degrees), the scapula abducts and upwardly rotates 1 degree for every 1 degree the humerus abducts.

SHOULDER JOINT RANGE OF MOTION

    The shoulder joint has a normal active and passive range of motion. This range of motion can be increased or inhibited in a number of ways; muscle weakness, muscle inflexibility and muscle injuries, to name a few. The following is the "normal" active and passive range of motion of the shoulder joint:

FLEXION = 180 degrees

EXTENSION = 50 degrees

ABDUCTION = 180 degrees

ADDUCTION = 40 degrees

INTERNAL ROTATION = 90 degrees

EXTERNAL ROTATION = 90 degrees

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April Ptak
Laina Hovsepian
SPME 400
Dept. of Sports Medicine, Pepperdine University