Discussing this in casual terms almost always causes men to cross their legs in response to the mere thought of this catastrophe. Even seasoned medical professionals cringe. Many physicians don't understand the underlying mechanism of this injury. Penile fracture can only occur with an erection. The vast majority of these injuries occur with sexual activity, although I have personally seen cases of a fractured penis that resulted when a man rolled on top of an erect penis while sleeping.
Penile fractures can also happen during masturbation.
In one case, a teenager who was masturbating forced his erect penis into his jeans at the fear of discovery and fractured it. The vast majority of patients are so embarrassed they will often manufacture elaborate stories. I have never seen a penile fracture in a man with a short penis. The symptom complex is fairly classic. Typically the partner is on top, the penis becomes dislodged from the vagina and in an attempt to reinsert it, the partner will come down on the penis, striking the symphysis pubis, the female pelvic bone, just missing the vaginal opening, and creating a sudden bending.