How do you get a hyper-extension in the knee or ankle?

Sport injury: A hyperextended knee injury occurs when the knee extends past a normal range of motion in the straight position. Essentially, the knee bends back on itself. Hyperextension can range from a mild injury, which is sore but heals in two to four weeks, to a severe injury requiring surgery and extensive knee pain medicines the ankle could be hyper extended in sport (dirt bike, on a rug ).