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Each joint in our body rests somewhere along a spectrum between joint MOBILTY and joint STABILITY. Though they are not always mutually exclusive, there is often a degree of trade-off between the two as you shift towards one end of this spectrum. Thus, for instance, the farther towards the MOBILITY end of the spectrum a joint falls, the less inherent joint STABILITY it will possess. Where each joint falls on this spectrum is determined largely by two factors:

  1. "Bony congruence" - how the bones in the joint fit together

  2. Soft tissue structural support (i.e. muscles, ligaments, joint capsule)

The shoulder joint is an incredibly MOBILE joint. As we’ve touched on in the past, the relationship of this joint resembles that of a large golf ball resting on a tee. This relationship allows for a great amount of shoulder mobility (just think how many different directions we can reach our hand in three-dimensional space around us). Yet, as the spectrum below indicates, with this added mobility comes the sacrifice of joint stability.

Our body’s answer to this need for added shoulder stability is a group of four muscles collectively known as the rotator cuff. With respect to this discussion, there is one crucial take home message:

The fundamental role of the rotator cuff is to work synergistically to promote humeral head centration during function. In other words, these four muscles need to fire and work together to keep the golf ball centered on the tee as you use your shoulder in daily life.

When the rotator cuff effectively functions this way, it allows the larger muscles (i.e. pec, lat, deltoid) to perform their chief task of moving the arm in space. Without proper rotator cuff activation, when these “big mover” muscles turn on to move the arm, the golf ball will end up sliding around on the golf tee. This creates a “shearing” motion between the ball and tee resulting in pinching pains and chronically achy shoulders. Moreover, and in my case, the more that golf ball slides on the tee, the faster those joint surfaces will wear on each other, no doubt causing an increased progression in osteoarthritis.

As the arthritis in my shoulder progressed and I continued to lose range of motion, I was constantly performing what I thought was shoulder “mobility work.” This typically involved me hanging from a pull up bar or grabbing a TRX/band and then yanking my body into some awkward position trying to force feed more mobility. While this may have provided some temporary relief, it never moved the needle for me long term. The key problem, regardless of which awkward set-up I was using that particular week, was that I was essentially only performing a passive stretch of one of the big movers of my shoulder, usually the pec or lat.

By continually stretching these “big mover” muscles, I was only addressing the byproducts of the problem, not the actual cause. Because I had such poor rotator cuff activation and movement patterns, the big mover muscles were constantly on and trying to stabilize the shoulder to compensate for my lack of rotator cuff contribution. Therefore, by constantly stretching the pec or lat, I may temporarily feel better after the stretch. However, once I stopped stretching and returned to function with the same faulty activation/movement pattern, the tension and overactivity of the pec and lat muscles would gradually return.

Techniques aimed at improving the flexibility of the big muscle groups of the shoulder certainly have a place in promoting shoulder health. However, it has become increasingly clear to me along this rehab path that passive flexibility it is not the end-all-be-all. Moreover, I believe it is proper rotator cuff function which is truly driving the bus on shoulder mobility.

There are a lot of branches and complexities in this thought process, so for digestibility I broke it into parts. The big takeaway from part I is understanding the critical role the rotator cuff plays in serving as the foundation for both shoulder stability and ultimately shoulder mobility. Stay tuned for some upcoming posts to unpack more on this.

Please get at me with any questions or comments on this first part, looking forward to the discussion!

Appreciate it y’all!


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