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.