John Thomas sign

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Positive John Thomas sign displayed by a patient who sustained a pertrochanteric fracture on the left.

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] One such study concluded that "The use of John Thomas sign remains limited to introducing humorous atmosphere in orthopedic meetings as the sign is clinically unreliable."[6] 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.[7]


  1. ^ "Note: "John Thomas" is an English language euphemism for "penis"
  2. ^ "Throckmorton sign". Radiopaedia. Retrieved 12 June 2015.  The Throckmorton sign is reportedly named for American neurologist Tom Bentley Throckmorton (1885-1961).
  3. ^ Thomas MC, Lyons BD, Walker RJ (1998). "John Thomas sign: common distraction or useful pointer?". Med. J. Aust. 169 (11-12): 670. PMID 9887926. 
  4. ^ Murphy, IG; Murphy CB; Hefferman EJ (April 2014). "John Thomas sign--a memorable but misleading sign in hip fractures.". Orthop Traumatol Surg Res. 100 (2): 199–202. doi:10.1016/j.otsr.2013.12.017. PMID 24582209. 
  5. ^ Jeys, Lee M.; Holton, Colin (23 December 2000). "Yorkshire men straight to the point, or not? Validation of the John Thomas Sign". British Medical Journal. 321 (1609). 
  6. ^ Ya'ish, Feras; Baloch, Khalid (2007). "John Thomas Sign: Truth or Myth?". Internet Journal of Orthopedic Surgery. 8 (2). doi:10.5580/854. 
  7. ^ Mouzopoulos GJ, Stamatakos MK, Mouzopoulos DJ (2007). "Does penis radiological shadow indicate the side of hip fracture?". J Postgrad Med. 53 (3): 217. doi:10.4103/0022-3859.33873. PMID 17700004.