Oh, the shoulder…where do I start? I previously addressed the shoulder movement pattern, but feel I need to explain the shoulder in a little greater detail here. This is not an anatomy lesson, so I don’t want to go into too much detail. Just know it is complex, very mobile but highly unstable and therefore subject to injury. It is comprised of the Glenohumeral joint (that is the typical ball and socket joint we traditionally think of), the Scapulo-Thoracic joint (where the shoulder blade rests on the rib cage), and the Scapulo-Clavicular joint (where the shoulder blade articulates with the collar bone – this is in fact the only place the “shoulder” is actually attached to your skeleton).
Now the “geeking out over anatomy” part is over. I must digress into the “even geekier physiology” part…I hope you all can bear with me just a little. Knowledge is power, and if you know a little more you will most likely be better suited to help yourself move and feel better! That is the ultimate goal, after all. Ok, back to the physiology:
You must understand that the humerus (big upper arm bone) only moves on the socket so far. The rest of the motion actually takes place when the scapula (shoulder blade) moves off the thoracic wall (rib cage). The scapula can actually move up to 60 degrees of the total 160-180 degrees of elevation you have in your shoulder. So, when you lift your arm up over your head, the shoulder blade moves about 1 degree for every 2 degrees your arm lifts. Of course this happens basically (not exactly) in this manner, but now you have a somewhat simplified break down of the mechanics. The diagram here is a great depiction of how this works – notice the way with scapula tilts. If the scapula doesn’t tilt but you keep reaching up with your arm, the humerus will run into that bone sticking out on top (called the acromion) and pinch the bursa and rotator cuff tendon (as seen in the first image above) and can result in pain.
So, now you can see how important the scapula is in regards to the mobility of the shoulder. Well, the scapula has 17 muscles that attach to it in a ton of differing angles! So, imagine how they effect the stability of the shoulder. These muscles all attach at odd angles & pull in so many different directions. If you think about it, the scapula is mostly just floating there. It is attached to your skeleton only by the tiny collar bone that is in the front of your body…and the actual shoulder blade is in the back. That is crazy, really – the scapula is just sitting there.
Anyway, THIS is the biggest area of concern that I see clinically: The difficulty trying to balance the stability of all of those muscles and various other fascia & ligaments that attach to it AND making sure you have appropriate mobility of the scapula. Not to mention addressing the mobility of the ribs & thoracic spine…remember, the scapula is just floating here and cannot move well if what it is sitting on top of (ribs/thoracic wall) is restricted. The shoulder blade can get glued down by immobility.
To show you all this, I am attaching some additional images. Many of the images I will be using show the complexity of the shoulder blade itself. Feel free to orient yourself, but know that there are deep and superficial layers, as well as front and back attachments that all pull on the scapula. To the top Left, you will see an image of muscles that move the shoulder blade. To the bottom Right, you will see an image of muscles that move the arm itself. All of these muscles directly or indirectly work on the scapula, though. You can see the muscle fibers and how they pull at different angles, too. In future posts, I hope to add more to the ball and socket shoulder (glenohumeral) joint. For now, the scapula gets the focus.
Like so much of the human body, resting position is not as important as dynamic/active motion. The scapula has to start in the right position, or at least not be mechanically disadvantaged, in order to best facilitate arm motion, though. What I see clinically is that people with shoulder pain struggle more often with scapular awareness and motor control. More specifically, patients do not know how to either retract/depress nor how to upwardly rotate effectively.
When in rehab, we often start to address this lack of motor control with the basics of both shoulder blades moving back into retraction, combined with depression (squeezing your shoulders back together and down). This needs to be short-lived, though as it seems to be more functional to retrain the shoulder blades with reciprocal (alternating) scapular activities – like how they are naturally used with walking, running, throwing, tennis or overhead hitting. In other words, one arm pulls while one arm pushes…counter-force/counter-balance.
So, once a person has gained this motor control with demonstrating the ability to move the scapula independently of the arm itself, they often have an immediate reduction in pain with just lifting the arm and are ready to start to train with greater force and velocity. Getting your body to achieve this motor control is where the meat and potatoes lies. Stay tuned!