Penile fractures are just as painful as they sound, and I mean that quite literally as one of the most distinguishable signs of the injury is an audible “crack.” A team of Brazilian researchers have dedicated months of their lives to recording instances of this traumatic injury in order to determine the sexual position most likely to cause it. In doing so, they discovered that the backward female on top, also known as the "reverse cowgirl," triggered the majority of the injuries.

In a study now published in Advances in Urology, the Brazilian researchers reviewed the cause, symptoms, and self-report of erection for men who had experienced a penile fracture. These fractures occur when the lining of the penis ruptures, when a blood-engorged penis is suddenly and forcefully bent. Due to the nature of the injury, it's most often sustained during sexual intercourse.

The data revealed some interesting correlations between sexual activity and likeness to experience this injury. For example, heterosexual intercourse was the most common cause, but the injury could also be self-inflicted via some sort of masturbation. As for sexual positions: "'Woman on top' was the potentially riskiest sexual position," wrote the authors. This pose was credited with being responsible for roughly half of all instances of penile fractures, followed by "doggy style," which accounted for 28 percent of cases. The remaining cases were described as having an "unclear" cause.

The review also revealed what some of the safer sex options may be. For example, homosexual intercourse was involved in only 12 percent of injuries. Interestingly, it seems that middle-aged Christian monks may have been onto something with backing the missionary position, as this pose was credited with the overall lowest incidence of penile injury. The authors wrote that with a man on top of the woman, as in the case with missionary, “he has better chances of stopping the penetration energy in response to the pain related to the penis harm, minimizing it.”

Perhaps the biggest discrepancy in the study was men’s unwillingness to disclose the nature of their injuries. Nearly a quarter of all patients questioned for this study refused to give any details as to how their fracture came about.

While sexual intercourse seemed to be the main cause of penile fracture in the West, in the Middle East, particularly in Iran, around half of all instances of penile fractures were caused by men trying to forcibly hide their erections. This may be due to the cultural practice of Taghaandan — Kurdish for “to click” — which encourages men to “break the Qholenj” by bending the tip of their erection until an audible click is heard. A separate study found the number of penile fractures in Iran caused by Taghaandan to be closer to 57 percent, explaining that a “direct blunt force or habitual clicking of the erect penis to achieve detumescence,[subsiding an erection]” was behind an overwhelming number of injuries in this part of the world.

Source: Reis LO, Carapatti M, Marmiroli R, et al. Mechanisms Predisposing Penile Fracture and Long-Term Outcomes on Erectile and Voiding Functions. Advances in Urology. 2014.