The woman-on-top position (also known as the reverse cowgirl position), where the woman aggressively thrusts up and down, is one of the high-risk positions for penile tunica albuginea rupture (commonly known as penile fracture), often listed as the "most dangerous" or "most prone to fracture" position. Many people hear a "snap," and their penis instantly goes limp and swells into a purplish-black eggplant shape. What is a "penile fracture"? Why is it so painful even when it's not a real fracture? Why does the woman-on-top position...