Testicular torsion happens when a testicle rotates and that rotation twists the spermatic cord, compromising blood flow to the testicle.
This restriction of blood flow can cause sudden and severe pain and swelling. Testicular torsion can happen at any age, but it is most common between ages 12 and 18. Testicular torsion is a medical emergency.
It is not clear why testicular torsion occurs and it is not a common problem. Physical activity does not in itself cause torsion, however, torsion may happen during exercise. Torsion may also happen while sitting, standing or sleeping.