Shoulder rotator cuff (RC) tears are a significant cause of pain and disability. Surgery is done to reconnect the torn RC tendon(s) to the bone. The goals of RC surgery are to decrease pain, and to increase range of motion (ROM) and strength. This is done arthroscopically; through a small incision in the patient's shoulder. After surgery, patients are usually placed in a sling for up to 6 weeks to protect the repaired shoulder tendons. During this time, ROM exercises are only done by using the un-operated arm for assistance. Voluntary or active shoulder movement is usually not permitted to allow the repaired tendons to heal. Unfortunately, some patients develop shoulder stiffness while wearing the sling, which can delay rehabilitation. Any delays in rehabilitation may result in reduced shoulder function, a slower return-to-work or daily activities, and may also impact the health care system, through increased use and cost of rehabilitation.