By Anthony Suminiski, Jess Stone and Mitchell Richards.

When the valves in the veins between deep and superficial veins become incompetent, the Venus pressure in the superficial veins rises relying on the skeletal muscles in the walls of the veins to expand in order to withstand the high pressure. When you are inactive your blood tends to collect in the lower parts of your body, often in your lower legs. This is usually nothing to worry about because when you start to move, your blood flow increases and moves evenly around your body. However, if you are immobile for a long period of time – such as after an operation, because of an illness or injury, or during a long journey – your blood flow can slow down considerably. A slow blood flow increases the chances of a blood clot forming

Symptoms of DVT in some cases of deep vein thrombosis (DVT) there may be no symptoms, but possible symptoms can include: pain, swelling and tenderness in one of your legs (usually your calf) a heavy ache in the affected area warm skin in the area of the clot redness of your skin, particularly at the back of your leg below the knee DVT usually affects one leg, but this is not always the case. The pain may be made worse by bending your foot upward towards your knee.

Your GP will ask you about your medical history and your symptoms. However, it can be difficult to diagnose DVT from symptoms alone, so your GP may recommend one of the following tests: An ultrasound scan can be used to detect clots in your veins D-dimer test A specialized blood test known as the D-dimer test is used to detect pieces of blood clot that have been broken down and are loose in your bloodstream. Venogram If the results of a D-dimer test and ultrasound scan cannot confirm a diagnosis of DVT, a venogram might be used. A special dye is injected into a vein in your foot, which travels up the blood vessels of your leg. An X- ray is taken to see the dye. If there is a blood clot in your leg, the dye will not be able to flow round it and will show up as a gap in your blood vessel.

Treatment You can treat DVT in a number of different ways. Treatment for deep vein thrombosis (DVT) aims to reduce the risk of, and if possible, prevent complications such as pulmonary embolism. A pulmonary embolism happens when the blood clot (or a piece of it that has broken off) travels in your blood to your lungs (see Complications of deep vein thrombosis). Treatments also try to relieve any symptoms of DVT, such as pain and swelling. People may need to go to hospital for treatment depending how bad their condition of DVT is.

Medication Anticlotting medicines help to stop blood clots getting bigger, or coming loose and travelling to your lungs. This anticlotting medicine is also used and helps to prevent new clots forming and is advised to take the medication at least three months after the clot has been treated. However if you are unable to take clotting medication, there is an alternative treatment. Your doctor may recommend a filter fitted in your inferior vena cava. A filter will prevent any blood clot that's been dislodged from travelling to your heart and then to your lungs where it could cause pulmonary embolism. Treatment of DVT

Compression stockings These are also called graduated compression stockings. They may reduce the risk of a getting another DVT or developing post-thrombotic syndrome You may need to wear them for at least two years after you develop DVT and you only need to wear them of the affected leg. Treatment of DVT