The Rotator Cuff

Unfortunately a friend of mine hurt his shoulder a wile ago and was having some issues when he was trying to climb, swim or do anything where lifting his arm over his head was a necessity.  He saw the doc and was diagnosed with a “Rotator Cuff” tear.

rotator cuffI hear this all the time, but the truth of the mater is that there are four muscles that make up this “Rotator Cuff.”  They are the Supraspinatus muscle, Infra Spinatus muscle, Teres Minor muscle and Sub Scapularis muscle (sometimes referred to as SITS).

So if there are four muscles and someone tells you you have a “Rotator Cuff” tear, which muscle are they talking about?  Well in most cases they are referring to the Supraspinatus muscle.  The main reason for this common occurrence is that when this muscle is torn it is very difficult to lift your arm past your shoulder.

I am going to go into the why because so many books and note cards don’t fully explain what its main purpose is:

” Contraction of the Supraspinatus muscle leads to abduction (the arm raising like in a jumping jack motion) of the arm at the shoulder joint. It is the main action is movement during the first 10-15 degrees of its arc. Beyond 30 degrees the Deltoid muscle becomes increasingly more effective at abducting the arm and becomes the main propagator of this action.”   This is typically where most books and cards stop.  Unfortunately if this was its only purpose then raising our arm above 90 degrees wouldn’t hurt.

“The Supraspinatus also helps to stabilize the shoulder joint by keeping the head of the humerus (arm bone) firmly pressed medially against the glenoid fossa (a flat bone on your shoulder blade) of the scapula(shoulder blade).”  This is what it really does.  However instead of stating it “helps” it should say “its main purpose . . .”  Yes its main purpose is to stabilize the humeru.  As you lift your arm up it actually pushes DOWN the head of the humerus so that you can actually lift your arm up with out pain!

I tried to illustrate this on the image, but you have this bone called the acromion.   It is at the very corner of your shoulder.  It basically makes a bridge over top of the tendon portion of the supraspinatus.  If the supraspinatus isn’t working properly then as you lift your arm up you pinch the muscle with that boney bridge.  I hope that makes since why it hurts, you are pinching it!

Unfortunately many times these tears have to be fixed surgically, but it is a pretty good recovery, usually around 6 month in total.  Typically you are doing ADLs (activities of daily living) in about 2 to 3 months.

I hope if nothing else you learned a little bit more about this Rotator Cuff mess and understand their are 4 muscles and the one most associated with the injury’s primary activity is to keep you from hurting yourself.


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