How do I know if I have a leg ulcer and what do they look like?

See picture. An ulcer is a break in the skin -- this can occur on the calf (typically due to venous disease) or on the toes (typically due to arterial disease).
Leg ulcers. An ulcer is an opening in the skin that looks like a hole. It can be large or small. Ulcers can be due to many reasons including diabetes, venous insufficiency and arterial insufficiency . The location of the ulcer often times suggest what the source of the ulcer is. Toe ulcers tend to be arterial or diabetic related and ankle ulcers tend to be venous. See a vascular surgeon for an evaluation.
It is a "sore" A leg ulcer is a break in the skin that is usually painful and tender. Ulcers around the ankle are usually from disease of veins, on the foot or toes usually from artery problems. Up higher in the leg there may be other things going on. if you have a sore on your leg that doesn't heal see a doctor, if possible a vascular surgeon.
Difficult to heal. Le ulcers occur spontaneously of as a result of injury. They are wounds in the skin which are difficult to heal.
See your doctor. Ulcers are usually draining and can be painful. See your doctor for an examination.