Way long time ago when bare back roamed the land.

A petit thing rode me till my dick was black and blue.  She would not quit even after I came.

Scared the shit out of me and I went to the ER.  The (female) doctor said no sex for a month and it would heal.  it did.  

Yes, it was worth it, but the gal disappeared on me, which they tended to do back then

..it is, oddly enough, my thighs. They can tighten up and spasm. It is is incredibly painful and the only cure is to jump off the bed and stomp my feet. I learned that trick when I ran track in High School. The best thing is to have my feet hanging off the end of the bed. Seems to ward it off pretty well.

I know someone who fractured his penis doing cowgirl with his SO. The lining inside his erect penis burst and required surgery to repair the damage. Needless to say, he said it wasn't a fun procedure to undergo, but it would have been even worse not having a fully functioning member.

I just hope that never happens to me, since cowgirl and reverse cowgirl are also my favorite positions.