Ankle sprains are a tearing of the ankle ligaments which have a good blood supply and swell alot.
Swelling/bruising occurs over the top/outside of the foot and ankle. It generally migrates to the foot and toes. A key thing is how long it takes to improve. Ankle sprains improve quickly, 1-2 wks. Treat first with rice and nsaid. If no improvement in 1-2wks, call pcp. Recurrent sprains can be issue.