Scapholunate advanced collapse (SLAC) was first described by Watson and Ballet upon identifying common radiographic patterns of arthritis in 210 wrists among 4000 radiographs. They described 3 stages of SLAC: arthritis that involves (1) the articulation between the radial styloid and scaphoid distal pole, (2) the entire radioscaphoid articulation, and (3) the capitolunate articulation. Others have described a fourth stage of radiolunate involvement in 14% to 83% of patients. Despite the universal presence of lunate dorsal tilt (ie, dorsal intercalated segment instability [DISI]), Watson and Ballet observed that the radiolunate joint was always spared arthritic involvement because of its congruence in all rotational postures. Importantly, patients with inflammatory arthritis were excluded from the analysis. However, subsequent authors have suggested that the definition be expanded to include crystalline arthropathy or scaphotrapezium-trapezoidal (STT) arthritis in the SLAC staging paradigm.