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Knee Pain

Deep Vein Thrombosis

Deep vein thrombosis (DVT) is a blood clot (also called a thrombus) that forms in a vein deep in the body. Most deep vein clots occur in the leg or thigh but can also occur in other parts of the body.

This clot may interfere with circulation and it may break off and travel through the blood stream and lodge in the lungs, causing severe damage to that organ. If the clot lodges in the lung, it is called pulmonary embolism (PE). This is a very serious condition that can cause death. DVT and PE are collectively called venous thromboembolism (VTE) and are predisposed by the same risk factors.


Anyone can develop DVT, but it becomes more common over the age of 40. As well as age, there are also some other risk factors, including:

  • having a history of DVT or pulmonary embolism

  • having a family history of blood clots

  • being inactive for long periods – such as after an operation or during a long journey

  • blood vessel damage – a damaged blood vessel wall can result in the formation of a blood clot

  • having certain conditions or treatments that cause your blood to clot more easily than normal – such as cancer (including chemotherapy and radiotherapy treatment), heart and lung disease, thrombophilia and Hughes syndrome

  • being pregnant – your blood also clots more easily during pregnancy

  • being overweight or obese

The combined contraceptive pill and hormone replacement therapy (HRT) both contain the female hormone oestrogen, which causes the blood to clot more easily. If you're taking either of these, your risk of developing DVT is slightly increased.


In some cases, there may be no symptoms of DVT. If symptoms do occur they can include:

  • pain, swelling and tenderness in one of your legs (usually your calf or thigh)

  • a heavy ache in the affected area

  • warm skin in the area of the clot

  • red skin, particularly at the back of your leg below the knee

DVT usually (although not always) affects one leg. The pain may be worse when you bend your foot upward towards your knee.


If a doctor thinks you have DVT (deep vein thrombosis), you should be referred to hospital within 24 hours for an ultrasound scan. The scan shows whether blood is flowing normally through the vein.

You may also have an X-ray of the vein (venogram). For this, you'll be injected with a dye to show where the blood clot is.

Non-surgical treatments


Your doctor might prescribe medications to thin your blood. The preferredTrusted Source treatment is with direct oral anticoagulants (DOACs) such as rivaroxaban (Xarelto) or apixaban (Eliquis).

Other drugs a doctor may use include:

  • heparin

  • warfarin (Coumadin)

  • enoxaparin (Lovenox)

  • fondaparinux (Arixtra) 

Blood-thinning medications make it harder for your blood to clot. They also keepTrusted Source existing clots as small as possible and decrease the chance that you’ll develop more clots. 

If blood thinners don’t work or the DVT is severe, your doctor might use thrombolytic drugs. People with upper extremity DVT may also benefitTrusted Source from this medication.

Thrombolytic drugs work by breaking up clots. You’ll receive these intravenously (through a vein).

Compression stockings

If you’re at high risk of DVT, wearing compression stockings can prevent swelling and might lower your chance of developing clots. 

Compression stockings reach just below your knee or right above it. Your doctor may recommend you wear these every day.


If you cannot take blood thinners, you might need a filter inside the large abdominal vein called the vena cava. This treatment helps prevent pulmonary embolisms by stopping clots from entering your lungs. 

Filters do have risks. If they’re left in for too long, they can actually increaseTrusted Source the risk of DVT. Filters should be used for a short-term period until the risk of thromboembolism is reduced, and blood thinners can be used.