How to Measure External Arm Rotation

The shoulder joint is a ball-and-socket joint that allows movement in all planes. External rotation describes the movement of the upper arm rotating outward. This motion is important for throwing, reaching back for a seat belt, washing your hair and getting dressed. External rotation is frequently decreased after injury to the rotator cuff muscles -- the dynamic stabilizers of the shoulder joint. Normal external rotation is 90 degrees at end-range and can be measured using a goniometer.

Things You'll Need

• Plinth table
• Large goniometer

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Instructions

• 1

  Instruct the patient to lay down on his back on the plinth table. Position the arm by bringing it out to the side at a 90 degree angle. Instruct the patient to bend his elbow to 90 degrees with his hand pointing toward the ceiling. This measurement can also be performed with the patient standing with his arm out to the side at a 90 degree angle, elbow bent to 90 degrees with his hand pointing straight forward.

• 2

  Place the axis of the goniometer at the tip of the patient's elbow. Align one arm of the goniometer with the patient's forearm and hold in it in place with one hand. Align the other arm of the goniometer perpendicular to the floor and hold it in place with your other hand. Use the same procedure to measure in standing.

• 3

  Instruct the patient to rotate his arm backward, keeping his elbow bent at 90 degrees. Continue to hold the arms of the goniometer in place as the patient moves. When the patient has moved to his limit, read the angle of rotation on the face of the gonionmeter. Use this same procedure to measure in standing.