Torsion of the testicle is an uncommon but serious condition in which the testicle twists on the cord that provides its blood supply. The twisting of this cord cuts off the blood supply to the testicle. It is extremely painful and must be treated immediately to prevent permanent damage to the testicle. Testicular torsion can happen after strenuous exercise or an injury, but it also can occur without any apparent cause. The condition can occur at any age but is most common between the ages of 10 and 20.