A shoulder orthosis is utilized to effect relative movement between bones in a body of a patient. The orthosis includes a base section which is connected with a trunk of a patient's body, an upper arm section which is connected with an upper portion of an arm of the patient, and a lower arm section which is connected with a lower portion of the arm of a patient. An interconnection between the base section and upper arm section of the orthosis is disposed beneath an axilla between the trunk and arm of the patient. A main drive assembly is operable to rotate the lower arm section of the orthosis relative to the upper arm section of the orthosis to pivot a humerus bone in the upper arm of the patient relative to a scapula bone in a shoulder of the patient. A secondary drive assembly is operable to move the lower arm section and upper arm section relative to the base section of the orthosis to move the upper arm of the patient into alignment with the shoulder of the patient.