A sprain describes an injury to a ligament caused by excessive stretching. The ligament can have tears in it or can be completely torn apart. Sprains occur most often in your ankles, knees or the arches of your feet.
Sprained ligaments swell rapidly and are painful.
Generally the greater the pain, the more severe the injury. For most minor sprains, you can probably treat the injury yourself. You can do this using anything from splints to crutches. R est the injured limb. But don't avoid all activity.