The John Thomas sign, [1] also known as the Throckmorton sign, [2] is a slang or joke term used in the field of radiology. It refers to the position of a penis as it relates to pathology on an X-ray of a pelvis. When the penis (visible on the X-ray as a shadow) points towards the same side as a unilateral medical condition such as a broken bone, this is considered a "positive John Thomas sign," and if the shadow points to the other side, it is a "negative John Thomas sign." [3]
Studies have shown that the "sign" is no better than chance at identifying the location of a hip fracture. [4] [5] In those cases where the John Thomas sign is positive, it has been proposed that a person with a displaced hip fracture may try to lie on the injured side to immobilize the fracture and reduce pain; the penis then inclines toward the downward (injured) side. [6]
Andy Murray, British professional tennis player, released a picture of his pelvic X-ray following his hip resurfacing surgery on January 29, 2019, [7] clearly demonstrating an example of a negative John Thomas or Throckmorton sign where his penis pointed away from the site of injury. The release of the X-ray image with visible genitalia was discussed by Piers Morgan on Good Morning Britain , prompting Murray, who was watching at the time, to message the show, stating, "Please can you stop discussing my genitals on national TV, I was heavily medicated at the time of posting." [8]
