Palmer Classification and Magnetic Resonance Imaging Findings of Ulnocarpal Impingement

Ulnocarpal impaction (UCI) syndrome is a well-recognized and relatively frequent cause of ulnar-sided wrist pain and limitation of motion. In the setting of negative or questionable negative radiographs and a strong clinical suspicion for UCI, magnetic resonance imaging (MRI) is helpful in detecting occult disease. Current MRI technology is capable of providing high-spatial-resolution images on multiple planes while manipulating contrast to highlight different tissue types. However, imaging of the triangular fibrocartilage complex has been challenging because of the small and complex components of this structure. In this article, the stages of UCI are discussed with illustrations of the spectrum of MRI findings using Palmer classification as a guideline.