Bruising and turning purple after a foot sprain is caused by subcutaneous blood stasis. In this case, the patient should take strict bed rest, elevate the affected limb, and apply brakes. If necessary, external fixation of the ankle cast or brace, then elevate the affected limb to help reduce swelling, apply cold compresses within 24 hours, and choose hot compresses or physiotherapy or baking after 48 hours. You can take oral medications to promote the swelling and bruising, such as Yunnan Baiyao Aerosol or Yunnan Baiyao Ointment, etc. You can also take oral Blood Mansions and Stasis Oral Liquid to make the bruising and swelling subside. If there is no relief within a short period of time, it is important to go to the hospital in a timely manner.