A low ankle sprain is the most common ankle injury, accounting for nearly 80% of all ankle injuries. It happens when your ankle rolls inward, stretching the ligaments that connect the bones on the outside of your ankle joint.  The medical term for this type of injury is called an inversion ankle sprain. The alternative to an inversion sprain is an eversion sprain. This happens when your ankle rolls outward, stretching the inside ligaments that connect the bones of your ankle joint.