Most venous ulcers occur on the leg, above the ankle.
Exactly why they favor that particular spot is not something this page can explain, and it won’t guess at a link that isn’t established here.
What is clear is how the disease works. The veins have one-way valves that keep blood flowing up toward your heart. When these valves become weak or the veins become scarred and blocked, blood can flow backward and pool in your legs. This is called venous insufficiency, and it leads to high pressure in the lower leg veins. The increase in pressure and buildup of fluid makes it harder for nutrients and oxygen to get to tissues, cells die, tissue is damaged, and a wound can form.
Lower leg veins is as specific as it gets. Pooling, pressure and the lower leg are all part of the picture; the ankle is simply where the ulcers appear.
What does show up at that site are the changes that come first. Fluid and blood cells leak out into the skin and other tissues, causing itchy, thin skin and skin changes called stasis dermatitis, an early sign of venous insufficiency. Along with it: leg swelling, heaviness and cramping; dark red, purple, brown, hardened skin, which is a sign that blood is pooling; and itching and tingling.
Those changes appearing around an ankle are the thing worth acting on, because they come before any sore does.
Location alone also does not identify a wound. Ankles are one of the places pressure sores tend to form, and ischemic ulcers may appear on legs, ankles, toes, and between toes. Three kinds of wound share that address.