Please tell me what happens to your muscles when you have a leg cramp?

Goes into a spasm -: Like into a knot, causing the person acute pain/discomfort till it starts to stretch out ( by meds, or massage, etc.). It can result from an injury to the muscle, a bone or a joint; lack of calcium is sometimes thought to be responsible for it; but generally no specific cause can be found for it, except when its from an injury.