Scapular movement during shoulder elevation

During shoulder elevation, the scapula must rotate upwardly.

Scapular upward rotation results from a sequence of shoulder girdle movements:

1. SCAPULA ROTATES UPWARDLY AS CLAVICLE ELEVATES,
   around an AXIS OF MOTION that passes through the SC joint and base of scapular spine

   Clavicular elevation continues UNTIL COSTOCLAVICULAR LIGAMENT BECOMES TIGHT.

2. AXIS OF SCAPULAR UPWARD ROTATION MOTION MOVES TO AC JOINT.

   The scapula continues to rotate upward at AC joint UNTIL CORACOCLAVICULAR LIGAMENT BECOMES TIGHT.

3. AS SCAPULAR UPWARD ROTATION CONTINUES,
   • Tension in the coracoclavicular ligament produces a passive force that rotates the clavicle backward.

   • Because the clavicle is shaped like a crank, backward clavicular rotation elevates the distal end of the clavicle and, with it, the acromion and the AC joint.

   • Elevation of the acromion and AC joint allows continued scapular upward rotation.

What forces drive these movements?

The Biomechanics Research Laboratory at Johns Hopkins University provides some helpful examples of animated passive motions. You may download these animated images from:

McFarland, E., Kato, S., Zerhouni, E. (2000). Shoulder joint kinematics. Biomechanics Research Laboratory, Johns Hopkins University. Retrieved November 13, 2000, from the World Wide Web: http://www.biomech.jhu.edu/projects/shoulder/

Software that plays .mpg files, such as Windows Media Player, is necessary to view these images.

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Last updated 11-13-00 ©Dave Thompson PT
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