Step 1: Decide what features to look for in a leg ulcer.
Leg ulcers are sorted by their site, edge, base and surrounding skin. Reading those four cues off the picture lets us assign the underlying cause.
Step 2: Identify the signature pattern in the image.
The ulcer sits over the lower leg, classically the medial malleolus (gaiter area); it is shallow with an irregular, sloping border; and the surrounding skin shows the stigmata of venous insufficiency - oedema, hyperpigmentation/haemosiderin staining and often varicose veins. This constellation is diagnostic of a venous ulcer.
Step 3: Differentiate from the other ulcer types.
• Arterial ulcer: on toes, heel or pressure points, painful, punched-out with a deep, well-defined edge and a poorly perfused base - not shallow or ankle-sited.
• Trophic ulcer: a painless, punched-out ulcer over a pressure/weight-bearing point from neuropathy - lacks the venous skin changes.
• Diabetic foot ulcer: over foot pressure points in a diabetic, mixed neuropathic-ischaemic, prone to infection - foot-located, not in the gaiter zone with venous staining.
Step 4: Conclusion.
A shallow, irregular ulcer at the lower leg/ankle with oedema and pigmentation points to chronic venous insufficiency.
Final answer: Option 2 - Venous.