Testicular torsion can happen from an injury, like being kicked in the groin, or from strenuous activity. Sometimes it can even happen for no apparent reason. With torsion, the cords holding the testicles in place can become twisted. This cuts off the blood supply to the testicle. The result is a lot of pain. The testicle also gets bigger, feels tender, and begins to swell. This is a medical emergency. It should be treated within six hours of when it happens. Sometimes, the doctor can treat it by untwisting the testicle. Sometimes surgery is needed. If it isn't treated, you could lose the testicle or lose its function.