What about that shoulder blade? The muscles around this important structure helps in the "heavy" loads of the shoulder and also the stability of it. If you don't have good movement of your shoulder blade, (approx 60 degrees) you can also have sticky shoulder motion. In fact, if you don't have good thoracic movement, your shoulder/arm muscles will start to get overworked, maybe even causing some tendonitis type issues.
So, that leaves us the actual shoulder joint (aka glenohumeral joint). This joint gives us a good 120 degrees of motion along with some motion in the clavicle. Without the other joints in play, we could actually have great motion here, and stuck in other places.
The last place folks don’t associate shoulder mobility with is the neck. If the neck is limited and/or the nerves that from the neck into the shoulder, this can limit you from raising that arm overhead.
Ok, got one more for you....guess what all the muscles have to do even with great motion? They have a particular "rhythm" to the motion. If one joint or muscle is out of rhythm, it can cause not just sticky shoulders, but other chronic conditions.
Next read: How to screen YOURSELF for issues
