This Chapter presents biomechanics of foot and ankle with a particular focus on biomechanics in sports, and the influence of surgical procedures on biomechanics. A thorough biomechanical understanding is necessary for successful treatment strategies for foot and ankle pathologies. Any treatment should aim to restore physiological biomechanics or get biomechanics as close to normal as possible. Impaired function and range of motion of joints of the foot and ankle overloads adjacent joints, disturbs gait and increases energy consumption. Certain sports require more than a physiological performance of the foot or overuse structures of the foot even when performed correctly and with an excellent and well-balanced technique and training schedule. In sports biomechanical demands on the foot and ankle are high. This is why even small deformities and abnormities that usually would not cause any problems can lead to overuse or make prone for specific injuries.