When conservative measures fail to relieve significant disability due to ankle joint disease, the only surgical method of treatment has been arthrodesis. Because of less than ideal results and other long-term problems with ankle arthrodesis, and after numerous investigation to characterize the ankle mechanically, we developed a prosthetic ankle joint replacement. The Mayo total ankle replacement is a metal-on-polyethylene, congruent, constrained prosthesis. Analysis of 94 patients (102 ankle prostheses) revealed good clinical results in patients with rheumatoid arthritis and in older persons with posttraumatic degenerative disease. Younger, more active patients in the latter category had more disappointing results. Further design development is under way to improve range-of-motion characteristics, decrease constraint forces, and improve bone fixation of the prosthetic components.