Older people who are obese, pregnant or smoke cigarettes or have recently undergone surgery are at an increased risk of developing a blood clot in the thigh or calf. Blood clot formation in a vein that is deep in the leg is a medical condition called deep vein thrombosis. Approximately 50 percent of people with deep vein thrombosis do not develop symptoms, according to The Merck Manuals Online Medical Library; however, people who experience symptoms of a blood clot in the thigh should consult a medical professional immediately.
When thick blood clots stick to the inside of a deep vein in the thigh, they can interrupt blood flow to the lower leg. As a result, blood accumulates above the location of the blood clot, causing extensive swelling of the upper thigh. This symptom of a blood clot in the thigh is called edema. People who develop this symptom can notice that their thigh appears unusually puffy or enlarged and pants or shorts may fit tightly around the affected thigh.
Blood accumulation in the thigh can cause swelling or enlargement of the vein that contains the blood clot. People can notice that a vein in the thigh appears to protrude from the skin due to inflammation caused by the blood clot.
Leg Pain or Tenderness
People with a blood clot in the thigh can experience sensations of mild to severe leg pain as a symptom of deep vein thrombosis. Sensations of pain may be worse when a person places weight on the affected leg, MedlinePlus notes. A blood clot in the thigh can also cause tenderness, especially when a person presses or touches the upper leg. Pain and tenderness typically persist and progressively become worse if the blood clot remains untreated.
Skin Discoloration or Warmth
The skin covering the site of the blood clot in the thigh can appear unusually red due to blood accumulation beneath the skin. People can also develop sensations of warmth throughout the affected leg or may notice that the discolored skin feels warm to the touch.
Chest Pain or Breathing Difficulties
Compared to blood clots in the lower leg or other body regions, blood clots in the thigh are more likely to detach from the vein and flow to the lungs, the National Heart Lung Blood Institute warns. A blood clot in the lungs is a life-threatening medical emergency called a pulmonary embolism. People who develop this condition as a result of a blood clot in the thigh can experience symptoms of chest pain or discomfort and shortness of breath. If these symptoms of a blood clot emerge, affected patients should seek emergency medical care.