A few months ago, I was stacking a large and heavy box in my mini-warehouse when I felt like the muscle in the top part of my left arm
the elbow to the shoulder - closer to the rotator cup). It really hurt a lot, and with time, although it feels better, it is still not perfect. It hurts when I twist my arm forward and it is sensitive in the rotator cup area.
It feels better when I take some Advil, but eventually the pain persists.