In the U.S., every year, 10,000 people receive ankle replacements. They are like an upside-down knee replacement and have been done with increasing frequency since the 1970s. They are composed of two pieces of metal, one in the tibia and one in the talus. There is an intervening polyethylene component that is either locked to the tibia or allowed to glide between the two metal components. In the beginning, deformities greater than 10 degrees varus or valgus were said to be contraindicated. Now, however, there are no deformities, in my opinion, that would negate an ankle replacement. The sophistication of ankle replacements is now complete with revision components. The most frequent diagnosis for receiving an ankle replacement is post-traumatic arthritis, about 80%. The remainder of the ankle replacements are done for metabolic diseases like gout, rheumatoid arthritis, and even hemophilia.