Ulnar palmar wrist pain near the pisiform produced by injury to PLC components that results in Pisotriquetral (PT) joint instability and subsequent arthrosis is known as Pisiform Ligament Complex (PLC) syndrome. A degenerative joint condition affecting the articular surfaces of the pisiform and triquetrum is PT joint osteoarthritis. The PT joint seldom develops primary osteoarthritis, and the majority of arthritic problems in this joint are post-traumatic in origin and preceded by chronic PT joint instability. The mechanism of PT joint osteoarthritis therefore cannot be understood in isolation because it overlaps and interacts with those of other diseases. Pisotriquetral Arthrosis (PTA) is a more catholic word for the arthritic diseases that affect this joint. Understanding the structure of PTA requires research into the anatomy and biomechanics of the pisiform and PT joint ligaments as well as the clinical subtypes of PLC syndrome.