Do testicles rotate when aroused?

I have noticed for a few years that I sometimes have a weird pain in my pelvic/testicle area. Not very often though. Maybe every couple of weeks or something. I noticed this after I had surgery a few years ago.

Anyway, I check for lumps, etc. and notice nothing. However, when I am fully erect I can feel a knot on the left testicle on the bottom which is coincidentally the larger of the two. Basically, my question is why can I feel it when aroused and not when flaccid? Do my testicles rotate around in there or something?

I am not asking for medical advice as I know that’s against the rules. I know I need to see a doctor about this as I am in the prime age range for testicular cancer.

sounds like a varacele …