<unk>  are<unk>  that have become enlarged and twisted. The term commonly refers to the<unk>  on the leg, although<unk>  occur elsewhere.<unk>  have leaflet valves to prevent blood from flowing backwards (retrograde). Leg muscles pump the blood in<unk>  to return it to the heart. When<unk>  become enlarged, the leaflets of the valves no longer meet properly, and the valves don't work. A common cause of valve failure is Deep<unk> Thrombosis (DVT), which can cause permanent damage to the valves.  The blood collects in the<unk>  and they enlarge even more.<unk>  are common in the superficial<unk>  of the legs, which are subject to high pressure when standing.
Varicose veins
Superficial vein thrombosis
Purpura
Venous claudication
Arterial thrombosis
Raynaud's phenomenon
Venous ulcer
Thrombophlebitis