If you have recently injured your ankle, swelling and bruising can indicate a bad sprain. Unfortunately, bruising and swelling can also indicate a broken ankle. If you had originally thought your ankle was sprained but you did not have an x-ray, it is important to monitor the condition of your ankle throughout your healing to make sure it has not actually been broken. Contact your doctor if you cannot walk on your ankle and are in severe pain, or if you think there's a chance your ankle could be broken.
Monitor your pain. If you can still walk on your foot, continue to walk on it and see if the pain lessens. If you experience severe pain while walking on your foot, stay off of it and limit your movements to pointing and flexing your foot, as you may have suffered a break. Although not being able to walk on your foot does not necessarily mean your foot is broken, do not overexert yourself just to be safe.
Check for bruising. Usually if you have a sprain, your foot will not bruise. If your foot turns red, purple or black in color, especially around your ankle, this is a sign your foot is broken.
Press on your ankle. If you are unable to place pressure on your ankle for an extended period of time without severe pain, you may have suffered a break.
Wait it out. Most sprains will improve greatly within 24 to 48 hours. If your ankle has worsened or the swelling has remained for more than 48 hours, you may have broken your ankle.
See a doctor for an x-ray. According to Dr. Lewis Maharam, a runners' doctor, "If there is any swelling after an ankle injury, please have it x-rayed." You cannot be 100% sure whether you have experienced a break without getting an x-ray, because hairline fractures and bone chips may otherwise be missed.