Triangular fibrocartilage complex tears
The Triangular Fibrocartilage Complex is a disc of tissue that sits between the ulnar head (the prominent bone on the little finger side of the wrist) and the wrist bones (the triquetral and lunate bone). It forms somewhat of a shock absorber function but also is very important in providing stability of the relationship between the two bones of the forearm (it helps to stop the two bones flopping one against the other). Tears of this ligament can come about either as a consequence of trauma (it tears away from the bone), or as a consequence of degeneration (it gets repetitively bumped between the ulnar head and the wrist bones) and so tears in a ragged, fluffy way.
If the tear is simply ragged and fluffy, debridement (excision of the fluffy parts) may improve the symptoms. If the tear is a traumatic one, then this will need repairing if simple splint treatment does not settle the discomfort.