--- title: Post-thrombotic syndrome description: What post-thrombotic syndrome is, why it develops after deep vein thrombosis, how it is recognised, which approaches to treatment and prevention clinical guidelines describe and when to see a doctor. type: disease aliases: - PTS - post-thrombotic disease - postphlebitic syndrome sources: - tier: guideline org: minzdrav-rf title: Тромбоз глубоких вен конечностей year: 2025 url: https://cr.minzdrav.gov.ru/view-cr/960_1 - tier: guideline org: minzdrav-rf title: Варикозное расширение вен нижних конечностей year: 2024 url: https://cr.minzdrav.gov.ru/view-cr/680_2 - tier: guideline org: nice title: 'Venous thromboembolic diseases: diagnosis, management and thrombophilia testing (NG158)' year: 2023 url: https://www.nice.org.uk/guidance/ng158 - tier: reference org: msd-manuals title: Chronic Venous Insufficiency and Post-Thrombotic Syndrome (MSD Manual Professional Version) year: 2026 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/peripheral-venous-disorders/chronic-venous-insufficiency-and-post-thrombotic-syndrome - tier: reference org: msd-manuals title: Chronic Venous Insufficiency and Post-Thrombotic Syndrome (MSD Manual Consumer Version) year: 2026 url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/venous-disorders/chronic-venous-insufficiency-and-post-thrombotic-syndrome sources_checked: 2026-10-14 review: null --- Post-thrombotic syndrome (PTS), also called post-thrombotic disease, is a long-term consequence of [deep vein thrombosis](../deep-vein-thrombosis/) (DVT). After DVT, irreversible changes remain in the vein wall and blood drains poorly from the leg: persistent swelling, pain and heaviness appear, the skin changes colour, and in the late stages venous (trophic) ulcers form. PTS can develop in many people who have had DVT — up to half of them, usually within 1 to 2 years. Together with [varicose veins](../varicose-veins/), it is classed as a chronic venous disease.

Normally, the leg muscles contract and push blood through the deep veins, and the valves in the veins let it pass only upwards, towards the heart, and stop it from flowing back.

After a clot, the vein wall thickens and remodels, and the lumen may stay partly blocked. Scar tissue can damage the valves: they hold blood back less well, and it flows back down the vein. Blood flow in the vein falls, the pressure in it rises, and fluid builds up in the leg, causing swelling.

 ## Why it happens A clot in a deep vein does not simply disappear: connective tissue grows into it, a channel reopens through it, and the vein wall thickens and remodels. Scar tissue left by the clot can damage the valves in the veins. As a result, blood flow in the veins falls, the pressure in them rises, and fluid builds up in the leg. Not everyone who has had a clot in the leg develops PTS. The risk is higher if the clot was in the upper part of the leg or in the pelvic area, if clots have recurred in the same leg, and in people with excess weight. The Russian Ministry of Health guideline describes how the thrombus evolves: fibrous organisation of the clot, its constriction, fragmentation and recanalisation, intimal thickening and remodelling of the vein wall; residual venous obstruction may persist after DVT. Chronic venous insufficiency occurs when venous obstruction, valvular incompetence or reduced contraction of the muscles around the veins decrease forward venous flow and increase venous pressure (venous hypertension). Prolonged venous hypertension causes tissue oedema, inflammation and hypoxia. PTS is symptomatic chronic venous insufficiency after DVT. According to MSD, risk factors for PTS are proximal thrombosis, recurrent ipsilateral DVT and a body mass index of 22 kg/m² or more; age and female sex are also associated with PTS. PTS is more common with more proximal and more extensive DVT, such as DVT involving the common femoral and/or iliofemoral veins. According to the Russian Ministry of Health guideline, upper limb DVT is associated with upper limb PTS in 25–77% of patients. In the aetiological part of the CEAP classification, PTS is a secondary disease with a known cause (Es) and affects the deep venous system, unlike varicose vein disease (Ep), in which the superficial veins are transformed. ## Symptoms The leg feels full and heavy, it aches and hurts, and there may be cramps, tiredness and tingling; all of this gets worse when standing or walking and eases with rest and when the leg is raised. The swelling is usually worse by the end of the day and goes down overnight while lying down. Later, the skin on the inside of the ankle becomes scaly and itchy and may darken: red blood cells leak out of the stretched veins into the skin. This skin is fragile: an ulcer can form even after scratching or a knock, and sometimes with no obvious cause, usually on the inside of the ankle. The symptoms of PTS can resemble those of an acute clot, and the condition noticeably limits activity and lowers quality of life. PTS always causes symptoms, whereas chronic venous insufficiency may cause no symptoms but always causes signs. PTS can range in severity from mild leg swelling to debilitating venous leg ulcers; moderate to severe disease develops in approximately 5–23% of patients. Venous stasis dermatitis includes erythema, hyperpigmentation, induration, venous ectasia, lipodermatosclerosis, lichenification and venous ulcers; the calf may be painful when compressed. Venous ulcers typically occur around the medial malleolus, are shallow and moist, and do not penetrate the deep fascia. Without adequate care of the legs, the disease can progress. ## How it is diagnosed The diagnosis is usually made from the symptoms and an examination. The doctor can assess how severe the condition is with the Villalta scale, which scores symptoms and signs separately for each leg. An ultrasound scan of the veins is done to make sure the swelling is not caused by a new clot. This matters because the symptoms of a recurrent clot can be mild and similar to those of PTS. In the Villalta scale given by the Russian Ministry of Health guideline, pain, cramps, heaviness, paraesthesia, itching, pretibial oedema, hyperpigmentation, venous ectasia, skin redness and skin induration are each scored from 0 to 3. Interpretation: 0–4 points — no PTS, 5–9 — mild, 10–14 — moderate, 15 or more or an ulcer — severe PTS. The absence of oedema with a reduced ankle-brachial index suggests [peripheral artery disease](../peripheral-artery-disease/) rather than chronic venous insufficiency or PTS. Oedema in chronic venous insufficiency tends to be unilateral or asymmetric; bilateral symmetric oedema is more likely to result from a systemic disorder, such as [heart failure](../heart-failure/). ## How it is treated Treatment is based on raising the leg and compression; medicines and surgery usually do not help much. Raising the leg above the level of the heart lowers the pressure in the veins. Compression — elastic bandages, compression stockings or intermittent pneumatic compression devices — reduces swelling and discomfort. Whether compression is needed, and what kind, is decided by the doctor. Exercise can help, especially exercises that strengthen the leg muscles and aerobic exercise. If an ulcer appears, wound care is important; once blood drains from the leg better, the ulcer heals, and wearing an elastic stocking after it has healed helps prevent a new one. MSD lists these approaches: leg elevation, compression (bandages, stockings, pneumatic devices), exercise training, topical treatments, treatment of secondary infection and sometimes surgical and endovascular procedures. Intermittent pneumatic compression is effective in severe PTS but is less practical than compression stockings for patients to adhere to on an ongoing basis. According to MSD, most medicines have little to no role in the routine treatment of chronic venous insufficiency. For severe symptoms, surgical venovenous bypass and endovascular venous stenting are options. ### Prevention Preventing PTS starts with treating the clot itself: lowering its risk is one of the aims of DVT treatment. People who have had DVT are given treatment that reduces blood clotting to prevent PTS; which treatment and for how long is decided by the doctor (for more, see the article on [deep vein thrombosis](../deep-vein-thrombosis/)). The Russian Ministry of Health guideline allows early removal of the clot in selected patients with extensive DVT to lower the risk of PTS, but does not recommend it for femoropopliteal DVT, because it does not affect the risk of PTS. Sources differ on compression stockings to prevent PTS. The Russian Ministry of Health guideline recommends elastic compression as early as possible after DVT is confirmed, to prevent PTS. NICE recommends not offering elastic graduated compression stockings after DVT to prevent PTS; this recommendation does not cover stockings used to relieve symptoms in the leg. The MSD Manual calls the data mixed: it includes stockings in prevention, but cites a meta-analysis of randomised trials in which stockings, compared with no stockings or sham stockings, did not significantly reduce the rate of PTS. The sources agree that compression relieves symptoms: according to the Russian Ministry of Health guideline, this is its main purpose after DVT; according to MSD, stockings reduce swelling, pain and tightness; and NICE does not extend its recommendation against stockings to their use for relieving symptoms. ## When to see a doctor If swelling or pain in the leg is new or has suddenly got worse, do not put it down to PTS and do not delay seeing a doctor: this may be a new clot, and its symptoms can be similar to those of PTS. The signs of a clot are described in the article on [deep vein thrombosis](../deep-vein-thrombosis/). If shortness of breath, chest pain, coughing up blood or fainting appear suddenly, call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK): this may be [pulmonary embolism](../pulmonary-embolism/). A very painful ulcer may be infected; this infection is treated too.