The incidence of complications in the initial three years' experience with total knee arthroplasty and patellar replacement was 9%. Of the total knee arthroplasties perforated in the last three years, neither fracture nor subluxation of the patella has occurred. A prosthesis with right and left femoral components and slight lateral (physiologic) slanting of the patellar groove is recommended. Lateral release is done only if absolutely necessary and is performed at a considerable distance from the patella to preserve blood supply. Excess bone removal from the patella is avoided. The fat pad is preserved in all cases. Patients who have undergone a patellectomy had a definitely weak knee. Treatment by simple immobilization failed to produce an excellent functional result.