Can you suddenly develop a venous leg ulcer without any previous symptoms of venous disease?

Yes: There may have been a prodrome and the c ulcer pops up. I need more medical information to answer your questions properly.

Chronic problem.: A venous ulcer is also called a venous stasis ulcer and this is a result of long standing chronic) venous insufficiency. There has to be a reason for the ulcer to form since it does not occur spontaneously. You should see a vein specialist for a full venous evaluation with a venous duplex exam of both the superficial and deep vein systems looking for reflux and old DVT.

Yes: Sometimes there is an isolated incompetent venous perforator vein under an ulcer. It may have been there for years and in retrospect the patient may remember pain in the area after exercise. When the skin above it can no longer compensate for the increased pressure, an ulcer can form.