What is post-thrombotic syndrome?
Post-thrombotic syndrome (PTS) is a long-term complication that can occur after a deep vein thrombosis (DVT) in the leg. It develops when the blood clot damages the valves in your veins, causing ongoing problems with blood flow.
This condition can make your leg feel swollen, painful, or heavy, and the skin may become discoloured or irritated. In more serious cases, it can lead to ulcers on the lower leg that are slow to heal.
PTS can develop weeks, months, or even years after a DVT. While not everyone who has a DVT will get PTS, it's quite common, affecting up to 50% of people with a history of DVT. That's why it's important to monitor your symptoms and seek medical advice if your leg doesn't feel right after a clot.
How post-thrombotic syndrome develops
Post-thrombotic syndrome develops as a direct consequence of the damage caused by a deep vein thrombosis (DVT). When a blood clot forms in a deep vein, usually in the leg, it can either partially or completely block blood flow. Over time, the clot can cause inflammation and scarring in the vein walls.
This damage affects the small valves inside the vein that normally help keep blood flowing in one direction up towards the heart. If these valves are weakened, scarred, or destroyed, they can no longer function properly. As a result, blood can begin to flow backwards or pool in the lower part of the leg, a condition known as venous reflux.
This ongoing pressure and congestion in the veins eventually lead to the hallmark symptoms of PTS: swelling, discomfort, skin changes, and, in severe cases, venous leg ulcers. The more extensive or untreated the initial DVT, the greater the likelihood that the veins will be permanently damaged, raising the risk of developing PTS.
Who is affected?
Post-thrombotic syndrome can affect anyone who's had a deep vein thrombosis, but you're more likely to develop it if:
- You had an extensive or unprovoked DVT (not related to surgery or travel)
- You’ve had more than one DVT in the same leg
- You didn’t get treatment promptly or consistently after your DVT
- You’re older, overweight, or have mobility issues
Although PTS is more common in older adults, it can also affect younger people, especially if they have underlying vein issues or risk factors that slow recovery from a clot.
Signs and symptoms of post-thrombotic syndrome
Symptoms of PTS usually affect the same leg that had the DVT. They can range from mild to severe and often get worse with activity or standing for long periods. Symptoms tend to develop gradually and may not appear until months after the initial clot. It's important to monitor any changes in how your leg feels or looks, especially if you've had a DVT in the past.
Common signs and symptoms
You might notice:
- Swelling: Ongoing or intermittent swelling in the lower leg or ankle
- Aching or heaviness: A tired, heavy feeling that worsens during the day
- Pain or cramping: Especially after standing or walking
- Skin changes: Redness, dark patches, or hard, tight skin
- Itching or tingling: Around the affected area
- Varicose veins: These may appear or worsen in the affected leg
These symptoms can interfere with your daily activities and, over time, may cause significant discomfort or even disability if not addressed.
When symptoms may worsen
Symptoms of PTS are typically more noticeable:
- Later in the day
- During hot weather
- After long periods of standing or sitting
You may also notice flare-ups during travel or when you're less active. Long car journeys or flights can make swelling and discomfort worse. Similarly, standing for extended periods such as at work or at events, can lead to heaviness or throbbing in the affected leg.
If left unmanaged, these repeated episodes can cause the condition to gradually worsen, leading to persistent discomfort, skin breakdown, or even open sores (ulcers) that are slow to heal. Spotting early changes and adjusting your routine, like using leg elevation or compression, can help keep symptoms under control.
Causes and risk factors
What causes post-thrombotic syndrome?
PTS is caused by damage to the veins following a DVT. The clot itself, or the body’s natural process of breaking it down, can scar the vein walls and valves. This stops blood from flowing properly and leads to increased pressure and pooling in the lower limb.
Risk factors you should know
Understanding your personal risk factors can help you take preventive steps and work with your healthcare provider to reduce your chances of developing PTS.
You may be more likely to develop PTS if:
- Your DVT wasn’t treated early or effectively: Delays in diagnosis or inadequate treatment can lead to more extensive vein damage.
- You have a history of multiple clots: Repeated episodes of DVT increase the overall damage to your veins.
- You’re older or have reduced mobility: Ageing veins are more prone to damage, and less movement reduces circulation in the legs.
- You’re overweight or obese: Excess body weight puts additional pressure on leg veins and can slow circulation.
- You have underlying vein disease or varicose veins: Pre-existing vein conditions make the veins more vulnerable to damage from a clot.
- The DVT was located in the thigh or pelvis: Clots higher up in the leg tend to cause more long-term complications.
- You’re not using compression therapy after DVT: Not wearing compression stockings when advised may contribute to worsening symptoms.
- You have other health conditions that affect circulation: Such as heart failure or chronic inflammatory diseases.
- You smoke: Smoking damages the blood vessels and increases the risk of clotting and vein damage.
Being aware of these risk factors can help you and your healthcare provider make informed decisions about monitoring, treatment, and long-term vein health management.
How post-thrombotic syndrome is diagnosed
Clinical examination
Your doctor will ask you about your past medical history, especially if you have had a deep vein thrombosis (DVT). They will want to know when the DVT occurred, how it was treated, and if you've had any previous vein problems. You'll also be asked to describe your current leg symptoms, such as pain, swelling, heaviness, or skin changes, and how these symptoms affect your daily activities and quality of life. This discussion helps the doctor understand the timeline and impact of your symptoms.
Diagnostic tests
To confirm a diagnosis or rule out other conditions, you may be offered:
- Duplex ultrasound: This imaging test checks blood flow and valve function in your leg veins.
- Venous pressure tests: Rarely used, but can assess how well your veins are coping with blood flow.
- Scoring systems: Such as the Villalta score, which helps rate the severity of PTS symptoms.
Treatment options for post-thrombotic syndrome
There is no cure for PTS, but treatment can ease symptoms and improve quality of life. Most treatments focus on improving circulation, reducing swelling, and preventing complications.
Non-invasive management options
- Compression stockings: These are often the first step. They support the veins and help reduce swelling and discomfort.
- Regular exercise: Walking and gentle leg movements help pump blood through your veins.
- Leg elevation: Raising your leg above heart level for short periods helps reduce swelling.
- Skin care: Keeping your skin moisturised and healthy can prevent irritation or breakdown.
Medication
Medication is not usually the main treatment for post-thrombotic syndrome, but it may be recommended in certain situations to help relieve symptoms or support recovery. Most patients will manage their condition with compression and lifestyle changes, but medicines can play a helpful role when symptoms flare or become difficult to control.
- Pain relief: Over-the-counter painkillers like paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may be used to manage discomfort. Topical anti-inflammatory gels can also provide localised relief.
- Diuretics: Occasionally used to reduce swelling by encouraging your body to get rid of excess fluid. However, these are not a routine treatment and are generally reserved for specific situations or short-term use.
- Anticoagulants (in some cases): If you're at risk of further blood clots or have ongoing clotting issues, your doctor may recommend continuing anticoagulant therapy (blood thinners). While not a treatment for PTS itself, this can help prevent complications.
It's important to follow your doctor’s advice when using medication. They will guide you on the best options depending on your overall health, symptoms, and the stage of your condition.
Surgical procedures
If symptoms are severe or not improving, your doctor may refer you for additional treatments. These are typically considered when supportive care and lifestyle changes are not enough to control swelling, pain, or skin changes, or if there is evidence of major vein damage on scans.
- Endovenous ablation: This minimally invasive procedure uses heat or laser energy to seal off damaged veins. It is often recommended when there is clear evidence of venous reflux (backward blood flow) in the superficial veins.
- Sclerotherapy: A special foam is injected into smaller surface veins to collapse them. This can improve symptoms and appearance, especially if varicose veins are part of your PTS picture. It's often used alongside other treatments.
- Venous stenting: If there is a significant narrowing or blockage in a deep vein, especially in the pelvis, a stent may be inserted to hold the vein open and restore normal blood flow. This is more common in people with severe symptoms and confirmed venous outflow obstruction on imaging.
These treatments are tailored to each person’s needs and are guided by detailed scans and clinical assessments. Your vascular team will explain the benefits, risks, and expected recovery time to help you make an informed decision.
Lifestyle management
There are some things you can be doing on a daily basis to help your wound heal and prevent your venous leg ulcer from getting worse:
- Leg elevation: Raising your legs when resting helps reduce swelling.
- Gentle exercise: Walking and ankle exercises improve circulation.
- Weight management: Reducing excess weight takes pressure off leg veins.
- Proper nutrition: A balanced diet supports wound healing.
Preventing post-thrombotic syndrome
The best way to prevent PTS is to reduce your risk of getting a DVT, or to treat DVTs quickly and thoroughly when they occur. Prevention is especially important for individuals who have already experienced a clot or who have known risk factors.
Lifestyle tips
Taking proactive steps in your daily life can make a real difference:
- Stay active: Regular movement helps blood flow and reduces clot risk. Walking, swimming, and leg exercises are all beneficial.
- Maintain a healthy weight: Carrying extra weight puts more pressure on your leg veins and can slow circulation.
- Avoid smoking: Smoking damages blood vessels and affects circulation, making clots and vein problems more likely.
- Stay hydrated: Drinking enough water can help keep your blood from becoming too thick, especially during travel or hot weather.
- Wear compression stockings: If recommended by your healthcare provider, these can help support blood flow and reduce swelling.
Early intervention
If you’ve had a DVT, prompt and consistent treatment is key to avoiding further complications:
- Continue anticoagulant treatment as prescribed: Taking blood thinners reduces the chance of another clot.
- Attend follow-up scans and appointments: Regular monitoring helps detect changes early.
- Use compression therapy: Wearing compression stockings consistently can lower the risk of developing PTS by supporting vein function.
- Stay informed and aware of symptoms: Knowing what to watch for means you can act quickly if problems arise.
By combining lifestyle measures with medical advice and regular check-ups, you can greatly reduce your risk of developing post-thrombotic syndrome or keep existing symptoms from getting worse.
When to seek medical advice
Signs you shouldn't ignore
Speak to a healthcare professional if you:
- Notice swelling or aching in a leg where you’ve previously had a DVT
- Develop new skin changes, such as redness or dark patches
- See signs of a sore or ulcer that won’t heal
Prompt advice can help manage symptoms and prevent complications like leg ulcers or chronic pain.
Doctors who treat this condition
Related
Chronic Venous Insufficiency
Deep Vein Thrombosis
Venous Leg Ulcers
References
- https://www.nhs.uk/conditions/post-thrombotic-syndrome/ [accessed 11.07.2025]
- https://www.nice.org.uk/guidance/ng89 [accessed 11.07.2025]
- https://thrombosisuk.org/ [accessed 11.07.2025]
- https://bestpractice.bmj.com/topics/en-gb/3000190 [accessed 11.07.2025]
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4013765/ [accessed 11.07.2025]
