A mild ankle sprain may heal itself in three days, but a severe sprain cannot heal itself in three days. 1. Self-healing: If the ankle sprain belongs to the mild, ankle joint did not appear obvious swelling, only mild pain symptoms. The patient actively cooperate with the brake rest, try to elevate the affected limb, not to the affected limb for weight-bearing, three days or so have the possibility of self-healing. 2. Can not be healed: If the ankle sprain is more serious, severe pain and swelling, usually about three days can not be recovered, but need a longer time. And this situation usually can not be self-healing, need to be related to the treatment, serious injuries require the use of supportive immobilization, and usually even surgical treatment can be recovered. After an ankle sprain, you need to actively consult a professional doctor for timely and proper treatment and therapy, to avoid delaying the condition, which is not conducive to recovery.