Pain behind the knee can indicate a blood clot in the leg, also referred to as deep vein thrombosis, according to Healthgrades. It is imperative for individuals with pain behind the knee that is accompanied by swelling or bruising to seek immediate medical attention.
Individuals with deep vein thrombosis are at risk for developing a blood clot in the lungs, also referred to as a pulmonary embolism, according to WebMD. Pulmonary embolisms occur when a portion of the blood clot in the leg breaks free and travels into the lungs. In certain cases, pulmonary embolisms do not cause any symptoms; however, if symptoms develop, individuals may experience severe chest pain, breathing difficulties and acute coughing.