A 63-year-old woman was referred because of decreased strength of her right leg manifesting with buckling of the knee for the past five years. Sometimes this led to falls, which made her feel insecure while walking. She experienced some aching in her right heel and in her right knee after long walks. She was able to walk for two hours. She and her husband loved to walk in the mountains, and during those hikes she used a cane. The previous history is relevant because at age 5 years she had suffered from poliomyelitis anterior acuta, which had affected both legs. She had a partial recovery in the sense that she regained normal strength of her left leg and was left with residual weakness of her right leg. She underwent surgery at age 10 years (ankle arthrodesis on the right and epiphysiodesis of the left leg).