How To Keep Your Arm From Ripping Off: Part I

There are many things that are taken for granted: spouses, family, health, homes, food, you name it!


Some rank math in the top ten of things we take for granted, which was likely ushered in by the National Council of Teachers of Math an organization, in itself, taken for granted.

Although health usually makes the list, body awareness and understanding never do. School House Rock reminds us that ‘knowledge is power’ and when it comes to your body nothing is more true. In this series of articles we will focus on the shoulder as it is an area of frequent injury.


****ALERT! You are about to embark on a journey that will increase your brain capacity. There will be anatomy along the way, do not be discouraged. It will be more along the lines of the song Dem Bones making this alert more like a Kmart blue light special.

Meet Your Shoulder

Your shoulder, the thing you shrug to get out of confessing, the place you look over when being discreet, an area…taken for granted! Welcome to where your arm attaches.That’s right, that big ball at the top of your arm is called the head of the humerus and it attaches to your shoulder in a shallow depression (glenoid fossa) that is part of your shoulder blade. You may be wondering the relevance of knowing this but the fact is the shoulder blade is only attached to your upper body (thorax) via the collar bone (clavicle) and nothing else! If you trace your collarbone out towards

the arm you will feel a protrusion, this is where the collarbone and the shoulder connect. That is it! Bones are like the studs of a wall, supportive. Your shoulder is fused to the main structure by one small attachment. Now before you go freaking out there are a couple of important things we must know about the shoulder.

The shoulder is the most freely movable joint. The shoulder is said to “sacrifice stability for mobility” (quote is from Anatomy Zone, a place for nerds like me). This means your shoulder is vulnerable to dysfunction and needs some TLC in the form of strengthening and stretching. It also means that your shoulder depends on your muscles to keep it secure.



Your arm comes out of socket when moving. Whoa! That does not sound right, but is true. In his book Applied Anatomy and Kinesiology; the Mechanics of Muscular Movement, William Pardon Bowen states: the “capsule is so loose it permits the head of the humerus to be drawn out of the socket about two inches, but the tendency of the weight of the arm to pull it far out is resisted normally by atmospheric pressure and by the tone of the muscles”. OK, so we have two things keeping our arm from dangling and that is 1. atmospheric pressure, or the weight of air on the surface of the arm, and 2. muscles. We are literally flirting with danger! In order for the shoulder to move in circles and rotate it needs to be able to come out of the socket slightly, otherwise we would be limited to up and down motions like Barbie and Ken. This makes for a complex joint as there are several muscles integral to the stabilization of the shoulder. These come in three separate groups. 

The Big Three

Up first is the popular group consists of the deltoids, pectoralis major (pecs), biceps, and triceps. Everybody knows these guys and is their friend. The back group comes in second and  includes the rhomboids, trapezius, and latissimus dorsi. These guys often fight for attention. Finally you have the rotator cuff group, these are actually four separate muscles and not a conglomeration as my grandmother believed (she also was plagued with ‘arthur’-itis versus the commonly known arthritis).

The next segment of our journey will explore the three groups of stabilizing muscles and introduce a shadowy figure hidden ominously behind a curtain like the Wizard of Oz. (mwuahahahahaha)