An arterial ulcer is a painful, deep sore or wound in the skin of the lower leg or foot. The ulcer doesn’t heal as you’d expect an ordinary sore to heal. That's because there isn't enough blood flowing to the area. Blood supplies oxygen and nutrients to the tissues.
The ulcer is usually found on skin over pressure points such as the tip of the toe, the heel, or the inner side of the ankle bone. Often it occurs where the skin rubs against clothing or shoes. It may also happen at the site of an injury, even a small one that you wouldn't expect to cause a problem. Sometimes the ulcer can start as a small dark spot that is painful and grows bigger.
If left untreated, the ulcer may lead to the death or decay of the tissue around the ulcer (gangrene).