There are two main things that can go wrong with veins of the legs:
• Blood can clot within the veins called thrombosis
• the valves can fail allowing blood to fall the wrong way down the vein
1 - clot in the Small Saphenous Vein (superficial thrombophlebitis)
If blood clots in the Small Saphenous Vein, it is called superficial thrombophlebitis. To break this phrase down:
• "Superficial" means that the clot is in the superficial veins in the fat and skin and not in the deep veins which would be more dangerous i.e. a deep vein thrombosis (DVT)
• "Thrombo" means a thrombosis or clot of blood that is still within a blood vessel, in this case the small saphenous vein
• "phlebitis" means an inflammation of the vein wall
The thrombus or clot in the Small Saphenous Vein causes intense inflammation in the wall of the vein and therefore in the surrounding tissues. This is often mistakenly thought of as infection and many doctors and nurses erroneously give antibiotics for this condition. The inflammation is actually nature’s way of trying to heal. For example if you banged your nose, it would go hot and red and get inflamed but it would not be infected. You would not expect to take antibiotics for this!
Nature uses inflammation to heal. It does this by getting more blood supply into the affected area so that there are more white blood cells which cause healing, taking away dead or injured cells and attacking any infection (if any is present).
Thrombophlebitis of the Small Saphenous Vein is clinically found as intense pain and tenderness of the back of the calf, usually in the midline. Sometimes a tender and hard "cord" can be felt which is the vein full of the clot. If the vein is near the surface, the skin can also be red and inflamed as a reaction.
2 - failure of the valves in the Small Saphenous Vein (Small Saphenous Vein or reflux)
If the Small Saphenous valves have failed, then blood can fall the wrong way down the vein. This is called venous "reflux" and the vein is therefore said to be "incompetent".
The problem isn't only that blood falls the wrong way down the Small Saphenous Vein, but as it is attached a deep vein, it also means that it allows blood to flow out of the deep vein and reflux back down the leg towards the ankle and foot. If it travels down at high speed pressure, this causes inflammation and damage to the skin, and can cause the tissue around the ankles to start ulceration. The body tries to prevent this by dilating side veins that are attached to the Small Saphenous Vein to make a "shock absorber" - these dilated veins are seen on the surface and are called varicose veins.
Therefore if Small Saphenous Vein incompetence (or reflux) is left to go on to cause damage to the skin at the ankle and foot, it may lead to discolouration and ulceration, or can cause varicose veins.