The typical case is a patient presents with trauma to the wrist and wrist pain. You do an x-ray. What do you think? This is a Scapholunate dissociation, also called rotatory subluxation of the scaphoid and sometimes knows as the Terry Thomas sign. It is a disruption of the scapholunate ligament with resultant instability. The cause is usually trauma and the complication is degenerative arthritis of the joint. The x-ray of the wrist will demonstrate a widened scapholunate space, usually greater than 4mm. This is best seen on a clenched fist view. Image from www.radiopaedia.com The scapholunate ligament is U shaped and divided into three compartments. A complete fear of the dorsal part, results in dissociation.
This is known as the Terry Thomas Sign for obvious reasons.