Deep vein thrombosis (DVT) is a blood clot in a deep vein in the body. They most often occur in the legs but can occur anywhere. They can have no symptoms.
Symptoms of a DVT:
Pain, swelling and tenderness at the site of the DVT
Heavy ache in the area
Warm skin in the area of the clot
Red skin at the back of your leg, below the knee
The pain may be worse when you bend your foot upward towards your knee
Symptoms are similar to a pulled muscle but are accompanied by swelling, discolouration and possibly warmth which are signs it may be a DVT.
Urgent treatment is required if you have a DVT. Doctors will use a doppler scan to measure the blood flow in your leg and decide if you have a clot blocking the flow.
Information from: thrombosisuk.org