Abstract: An improved orthosis provides mobilization of the shoulder joint and arm in a wide variety of clinically useful positions and also optional controlled movement of the forearm over a selectable range in the vertical plane. The orthosis has waist securing and harness means for securing it to the human body. A rise and fall mount attached to a waistband supports a pivoting slide and a forearm support assembly which includes a hand support. An arrangement of slides and adjustable securing means is so disposed as to allow the shoulder orthosis to be configured rapidly, easily and in a continuously variable manner for rigid, stable immobilization following injury or surgery.