Sprained foot turned purple may be caused by subcutaneous bruising, the patient should rest in bed, cold compresses within 24-48 hours, hot compresses after 48 hours. If necessary, go to the hospital for ankle cast external fixation. The foot sprained purple shows in the sprain, local bleeding, resulting in subcutaneous bruising, slowly bruising blood will seep into the skin, coupled with venous reflux, bleeding triggered by the purple. 48 hours later, the patient can let family members and friends to help themselves to do a little foot hot compresses, you can let the bruising subside. Patients should rest in bed, lying in bed when you can lift the affected limb a little bit, which is conducive to venous return, reduce swelling. The patient can take some drugs under the guidance of the doctor to activate blood circulation and remove blood stasis, if the purple, swelling has not subsided, then we have to see if we need to carry out external fixation of ankle plaster under the advice of the doctor.