John Thomas sign

The John Thomas sign, also known as the Throckmorton sign, is a term that 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.
The sign is employed as a humorous aside. A mistaken assumption has been proposed as a possible explanation: rather than the penis actually pointing to one side, "the anteroposterior view of the pelvis is in fact an oblique view, which shows the fracture and the penis shadow on the same side." Genital asymmetry correlates with handedness, and a relationship between handedness and injury has been proposed as a mechanism for the sign.<ref name="pmid9887926"/>

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