my knot is on my right shoulder blade and is from computer work and sleeping in the wrong position, aggravated when riding. Someone posted a great thought pattern (sorry can't remember who or when) about thinking about putting your shoulder blades into your back pocket. I have found that helpful when riding.
Exercises - raise both arms out in front of your body, keep shoulders level and relaxed. Reach out with one arm at a time- which moves your shoulder forward, keeping elbows locked.

#2 raise arms in front of body, bend arms at elbows 90 degrees. palms together and forearms together, place your thumbs on your forehead and lift your elbows toward the sky, w/o tilting your head or arching your back.
#3 stand in a door way, reach up and back to grab the frame (you will be adjusting your body, forward and at angles) as you are holding onto the doorway with your arm fully extended, turn your body to feel the pull across your chest, hold for two seconds and repeat, start low and continue higher as your arms & chest loosen up.
Good luck!