Venous ulcers (venous insufficiency ulceration,<unk> s,<unk>  dermatitis, varicose ulcers, or ulcus cruris) are wounds that are thought to occur due to improper functioning of venous valves, usually of the legs (hence leg ulcers).:846  They are the major occurrence of chronic wounds, occurring in 70% to 90% of leg ulcer cases. Venous ulcers develop mostly along the medial distal leg, and can be very painful.
Two layers of skin created from animal sources as a skin graft has been found to be useful in venous leg ulcers.
Stasis ulcer
Aphthous ulcer
Buruli ulcer
Venous ulcer
Tropical ulcer
Hunner's ulcer
Stress ulcer
Genital ulcer