A blood clot in leg can sometimes be difficult to recognize because symptoms may vary. A deep vein thrombosis (DVT) may cause swelling, pain or tenderness, warmth, or changes in skin color, typically affecting one leg. Certain factors, including prolonged immobility, recent surgery, or a history of blood clots, can increase risk. At USA Vein Clinics, vein specialists can evaluate symptoms and help identify underlying vein conditions.