It was just the other day during a casual conversation with one of my clients, when I realized we can all stand to benefit from a little lesson on the shoulder’s structure, its actions and dysfunctions. We discussed the importance of internal humeral rotation which can often be overlooked due to the fact that so many of us present considerably protracted, elevated, and internally rotated already. Many thanks to the 40 hours a week we spend at a computer, texting on our phones, and those of you that are cobblers that will do the trick too. I hear this line from someone at least once a month in an effort to describe their discomfort, “ I have rotator cuff” it’s right up there with my other favorite “I have TMJ” my usual reply is “good you’re going to need that you should hang on to it”. But seriously let’s take a look at rotator cuff 101, the basic structure, its actions and dysfunctions.
The rotator cuff is comprised of four muscles and there trendiness insertions that share a small pace of real estate at the head of the humerus. Known as the S.I.T.S. group the muscles are as follows: Supraspinatus, Infraspinatus, Teres Minor and Subscapularis. Each muscle of the S.I.T.S. group has a primary action. Supraspinatus abducts the arm, elevating your arm away from the body out to the side. Infraspinatus and Teres Minor both externally rotate the arm, with the arm at the side of the body, hand in a neutral position it moves your cubital fossa or the “elbow pit” from facing the side of the body to facing forwarded or away from the body. Subscapularis internally rotates the arm, moving the cubital fossa from facing the side or front to the back of the body or side. The rotator cuff is not only responsible for the actions and movements described above but they help provide stability in any combination of positions that the shoulder experiences loading. Whether it is bodyweight holding your hand high on the steering wheel or for my Olympic lifters trying to find that perfect overhead position when performing the snatch, a healthy stable rotator cuff is essential. The activity of throwing or for my CrossFiters controlling the bar from overhead to the high hang or to the floor has a unique effect on the shoulder. The larger muscles of the anterior shoulder combined with a much greater end range for horizontal adduction/medial rotation can result in tremendous eccentric loading of the posterior rotator cuff, Infraspinatus and Teres Minor. So it’s possible that some of the pain experienced in the posterior rotator cuff is not due to short hyper-tonic muscles but long, inhibited, and often weak muscles.
This is a simple depiction of the rotator cuff and the boney structures it interacts with.
One of the dysfunctions associated with the rotator cuff is a supraspinatus strain. The supraspinatus can be compressed against the underside of the Acromion Process. Repeated compression can result in degeneration of the muscle tendon unit leading to tearing of the associated fibers and further resulting in tendentious then calcific tendinitis. Another factor in supraspinatus dysfunction is a decrease in profusion to the area due to its limited vascularity. This fact alone leaves the area more vulnerable to injury, slower healing, and recovery times. The majority of injury’s involving the infraspinatus and teres minor are the result of mechanical loading during eccentric contraction or lengthening under load as the powerful adductors, protractors, and internal rotators of the humerus propel the arm forward and internal. It’s the posterior rotator cuff’s job to decelerate the arm if the momentum is too great or the force is too severe. The posterior rotator cuff can sustain injury especially if the muscles are inhibited and weak. The injuries sustained by the infraspinatus and teres minor are similar to those sustained to the supraspinatus with a decrease in profusion but with the added stress of an agonist group that can produce more force resulting in muscle tendon strains, tendentious and possible fiber tearing. The subscapularis has the lowest rate of injury in the rotator cuff as it shares its prime movement with larger and more powerful muscles such as pectoralis and latissimus dorsi; teres major plays a supportive role as well. Although the subscapularis has this added support it does sustain injury and tears which are commonly accompanied by more serous injures like gleno humeral dislocations. Other pathology’s coupled with rotator cuff dysfunctions can include reflex muscular inhibition; this can affect biomechanical balance needed for proper movement and range of motion. The shoulder is a confounding joint, what the bumblebee is to physics the shoulder is to kinesiology. It is amazing the shoulder works at all. As for stretching and mobilization methods I feel it would be a disservice to try and explain the appropriate technics and methods needed to effect real change. That’s best demonstrated one on one since everyone’s anatomy or kinetic chains do not behave in the same way. Stretching and mobilizing are a lot like buying a Rolex in Chinatown it may look like the real thing but won’t preform or have the same effect as the immaculate and precisely designed authentic.
Orthopedic Manual Therapist, CMT
CrossFit L1 Certified
CrossFit Olympic Lifting Certified