In the previous post we went over the primary role of the rotator cuff (RC) which is to stabilize arm within the socket of the shoulder blade. There are four muscles that make up the RC: the supraspinatus, infraspinatus, teres minor and subscapularis (you can use the pneumonic S.I.T.S. to remember them more easily). Below we take a look at what biomechanics movements they’re responsible for and how you activate them throughout the day:

S: Supraspinatus – primarily functions to raise the arm out to the side up to shoulder level

I: Infrapsinatus – primary function is external rotation (i.e. position your arm up to scratch the back of your head)

T: Teres Minor – primary function is external rotation similar to the infraspinatus above

S: Subscapularis – primary function is internal rotation (i.e. positions the arm to reach the back pocket or bra strap)


If you find yourself having pain or difficulty with any of these movements, there is a good chance that there’s a dysfunction occurring either directly with the shoulder joint or surrounding areas that further impact the shoulder joint (such as the spine).

The shoulder joint is one of the most common places of injury because of the MASSIVE amount of motion available from this ball-in-socket joint. Plus we use it every day to drive, cook, clean, and work. If these muscles aren’t strong and functioning cohesively within the joint, overtime it can result in impingement, tendonitis and muscle tears. Next we’ll take a deeper look at these impairments and how we can treat/prevent worsening of symptoms.