Outcomes of surgery for a rotator cuff tear depend on a wide range of factors. Patient age, duration of symptoms, and time from injury to surgery can make a difference. Even more important is the type and severity of injury.
Most rotator cuff tears affect the supraspinatus tendon. If the force of the injury is enough, the tear can extend posteriorly (backwards) to include the supraspinatus tendon.
Less often, the subscapularis tendon is injured. If the force is great enough, the tear extends anteriorly. The long head of the biceps can be damaged. This causes a condition called biceps tendon disorder.
Early surgical repair is advised for tears that extend through half (or more) of the tendon. With no delays in treatment, there is less muscle atrophy, less fatty infiltration of the tendon/muscle unit, and less scarring in the area.
After three to six months from the time of the injury, pain and loss of motion are signs that surgery is still needed. More than six months after the injury, the surgeon will want to re-evaluate the shoulder and see if the tear can be repaired. Sometimes severe tears cannot be repaired. Instead, shoulder rehab is needed to regain as much motion and function as possible.