Hi,
You may be referring to a
leg cramp which presents as an acute
pain originating from a muscle in the
leg, in one of the calf muscles, below and behind the knee or small muscles of the feet. In most cases, leg cramps occur when you are resting especially while sleeping or when you wake up. This is caused by a contraction of an already shortened muscle. So, contracting the leg further may cause the muscle to go into spasm. It happens frequently during sleep.