The rotator cuff is made up the "SITS" muscles (supraspinatus, infraspinatus, teres minor and subscapularis). These small muscles are important in stabilizing the shoulder joint. The shoulder is classified as a "ball-in-socket joint," but the ball is large and the socket is shallow, somewhat like a golf ball on a tee. The rotator cuff muscles fight to keep the ball on the tee while larger muscles move the arm at the shoulder joint. Without the stabilizing efforts of the rotator cuff, routine movements would easily dislocate the shoulder. Injury to the rotator cuff tends to cause certain signs and symptoms.
Pain
Injury to the rotator cuff is a common source of pain in the shoulder. The pain is typically in the front or side of the shoulder. Certain movements or positions of the shoulder can intensify or reduce the pain. You are more apt to readily identify positions of provocation than to point specifically to a precise location as the source of pain. It is usually raising the arms above shoulder level that increases the pain, which can be achy to sharp in quality and annoying to severe in intensity, depending on the nature and severity of the injury.
Weakness
Because of its anatomical location, the supraspinatus is the most vulnerable of the SITS muscles. A 2007 study in the journal "Modern Rheumatology" confirms that the supraspinatus is the most commonly injured muscle/tendon of the rotator cuff. This muscle assists in the movement of raising the arm away from the side of the body. Weakness of this muscle may be noticed when performing a task like putting on a coat or reaching out and pouring from a pitcher.
Reduced Mobility
Due to pain, weakness and compromised stability of the shoulder with an injured rotator cuff, normal movement of the joint is usually not possible. It may be possible for another person to "passively" move your relaxed shoulder through a fairly normal range, but when you attempt to "actively" move your shoulder under its own power, it may not perform well. With a damaged rotator cuff, it may be difficult to reach the arm overhead. If you stand in front of a mirror, you may notice the affected shoulder shrugging instead of moving like a hinge as the body tries to substitute other muscles to assist in this movement. With the back of the hand resting on the small of the back, it may be difficult to push the hand away from the back with certain rotator cuff injuries. This is described as a positive "Lift-Off" test in the orthopedic literature. According to a 2009 article in the French journal "Joint, Bone, Spine," a positive Lift-Off test is a fairly specific finding for these injuries.
References
- "Modern Rheumatology;" Ultrasonographic Findings of Painful Shoulders and Correlation between Physical Examination and Ultrasonographic Rotator Cuff Tear; H.A. Kim, S.H. Kim, Y.I. Seo; June 2007
- "Joint, Bone, Spine;" Contribution of Clinical Tests to the Diagnosis of Rotator Cuff Disease: A Systematic Literature Review; J. Beaudreuil, R. Nizard, T. Thomas, et al.; January 2009
