The pathologic examination of failed joints, whether natural or artificial, is an indispensable part of the understanding of arthritis, as it is the last, and still best opportunity to determine or verify the correct diagnosis. Accuracy in pathologic diagnosis, based on a firm understanding of the various disease processes, provides reliable data for use in clinical registries, provides an opportunity to explain the “unusual” clinical presentation, and ultimately gives the “best evidence” for basing further treatments and prognosis for the individual patient.