These fractures occur either via direct blow to the dorsum of the hand or a fall on an outstretched hand causing extreme dorsiflexion resulting in impaction of the ulnar styloid against the triquetrum. 

    Physical examination reveals localized tenderness over the dorsum of the wrist just distal to the ulnar styloid.  The triquetrum is best palpable when the hand is deviated radially.  Swelling may be noted in that area and patients may have limited wrist motion.