NEW YORK (CBSNewYork) – Doctors in the Bronx say they encountered one of the rarest medical mysteries they’ve come across – a man’s penis was literally turning to bone.

According to a team of physicians from Lincoln Medical and Mental Health Center, a 63-year-old man suffered a fall onto the pavement and went to the hospital complaining of knee pain.

“He was walking on the side walk with his cane when he fell onto his buttocks. Shortly thereafter, he started to have a left knee pain,” the doctors reported in the medical journal Urology Case Reports.

To see the x-ray pictures click here

Doctors did an x-ray on the 63-year-old’s pelvis to make sure he hadn’t hurt his hip as well and that’s when the stunning discovery was made.

“An extensive, plaque-like calcification along the expected distribution of the penis was evident.”

The Bronx doctors say the unidentified man was likely suffering from an “exceedingly rare” case of ossification, or the abnormal formation of bone.

“Penile ossification remains a relatively rare condition being mentioned in very few journals,” the Bronx doctors said.

There are reportedly less than 40 published cases of a man’s penis turning to bone in this way.

Unfortunately, the staff at Lincoln Medical could not examine the man’s pelvic paralysis further. The 63-year-old reportedly decided to leave the hospital against the advice of medics and a follow-up lab exam could not be done.

For now, a medical mystery is still walking around New York.