Ligaments are elastic bands that stretch—within limits—to protect the ankle joint from abnormal movement such as twisting, turning, or rolling. When a ligament is stretched too far, however, it sustains a sprain. In severe sprain cases, the ligament can actually tear. Some people may hear a popping sound following an ankle sprain and all experience pain, swelling, and an inability to place pressure on the injured foot. The swelling and pain typically last two to three days, depending on the severity of the injury. However, the full recovery process takes about four to six weeks. During this time, the ankle should be protected, but may require some motion to avoid stiffness. For a Grade 1 or 2 sprain, professionals recommend RICE (rest, ice, compression, and elevation). A Grade 3 sprain can result in permanent instability. While surgery is rarely necessary, a leg cast or cast-brace may be. Physical therapy can help to restore range of motion, strength, and flexibility following a sprain. It also can help prepare individuals for a return to normal activities—first, to ones that do not require turning or twisting and then to ones that require sharp, sudden turns, like tennis, basketball, or soccer. Physical therapy also involves prevention education, including warm-up exercises and stretches.