In spite of advance in knowledge and the great increase in surgical operations with their consequent revelations, there are many diseases of the knee joint that cannot be diagnosed definitely. The study of pathologic specimens which include the entire joint is of significance, but such specimens are relatively rare. The knee joint is seldom examined at necropsy, and various surgical procedures, although affording macroscopic examination, give little material for pathologic research. The operation of resection, however, makes it possible to secure a large enough specimen so that a conception may be formed of the pathologic changes in the joint. The important structures of the joint are all included in such specimens and they can be studied collectively to visualize a definite picture of the changes present. Resection has been performed extensively at the Mayo Clinic for many years, during which valuable data have accumulated. MATERIAL STUDIED Records of 236 resections