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Last updated Friday, February 04, 2005
Resting stability
It is apparent that the relaxed glenohumeral joint is held together without either active muscle contraction or ligament tension. The intact shoulder of a fresh anatomical specimen (Kumar and Balasubramaniam, 1985a), the anesthetized and paralyzed shoulder of a patient in the operating room, and the arm relaxed at the side (Basmajian and Bazant, 1959) all maintain the normal relationships of the glenoid and humeral joint surfaces. This resting stability is due to a group of mechanisms including adhesion/cohesion, the glenoid suction cup, and limited joint volume. These mechanisms save energy as was pointed out by Humphry in 1858 (Humphry, 1858): "We have only to remember that this power is in continual operation to appreciate the amount of animal force that is economized."
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