The post-thrombotic limb follows a deep vein thrombosis. A post-thrombotic syndrome takes, on average, 10 years to develop from the initial vein damage. The condition is characterised by swelling, pain, a feeling of heaviness and skin discolouration, the skin initially becoming red and then turning brown. The skin then becomes thickened (lipodermatosclerosis) and, finally, the patient may develop an ulcer. In a normal patient, walking is brought about by muscle contractions. As the muscles contract, the veins are compressed;. the presence of valves in the veins allows the blood to be forced back to the heart. In a patient with normally functioning valves, walking therefore results in a reduction of venous pressure. If the valves are damaged when the vein is compressed, blood is forced both up and down the leg. Forcing the blood down the leg results in the venous pressure being maintained or increased. As a result of this maintained venous pressure (venous hypertension), fluid and cells leak from the capillaries into the surrounding tissues. This initiates a reaction within the tissues, which leads to the deposition of fibrin and the activation of white blood cells. This process then leads on to scarring and skin breakdown, leading to ulceration. A patient who has had a deep vein thrombosis may complain that their leg feels heavy. They will notice the symptoms get worse if they stand a great deal. They will find it difficult to walk great distances and may end up performing a sedentary rather than an active job. The appearances of the leg may cause some concern. Currently treatment involves wearing a heavy elastic compression stocking. Attempts at repairing deep vein valves have been tried but the results are, overall, disappointing. If the patient goes on to develop an ulcer, they will require frequent dressings. Ulcers can be extremely painful, although the pain is usually associated with infection. Once a patient develops an ulcer, they will require frequent dressings and may require admission to hospital for surgical debridement of the wound, followed by split skin grafting.