In chronic arthritis, arthroplasty of the knee involves a number of problems which do not occur in other diseases. Nylon membrane has been found to be non-irritating and durable and has proved to be a satisfactory material to place between the articular surfaces. The indications for arthroplasty are not exact but are dependent upon the degree of disability of the arthritic patient. The commonest postoperative complications is restriction of flexion. A satisfactorily functioning knee was obtained in fifty-eight of seventy arthritic knees subjected to the procedure described herein.