Chronic Venous Insufficiency: This condition is a common cause of lower extremity swelling, especially in older adults or those with a history of deep vein thrombosis. It occurs when the veins have problems returning blood from the legs back to the heart due to issues like faulty valves.

Heart Failure: Swelling in the legs can be a sign of heart failure, where the heart is not pumping efficiently, leading to fluid buildup in the body.
Kidney Disease: Kidney problems can lead to fluid retention, causing swelling in the legs.
Liver Disease: Conditions like cirrhosis can cause fluid buildup in the body, leading to swelling in the legs.
Lymphedema: This is a condition characterized by the abnormal collection of protein-rich fluid in the interstitial tissue, leading to swelling of one or more extremities.

Deep Vein Thrombosis (DVT): Although not the most common cause, DVT is a potentially life-threatening condition that requires immediate medical attention. It involves the formation of a blood clot in a deep vein, typically in the legs.
Cellulitis: A bacterial skin infection that can cause swelling, redness, and warmth in the affected area. If not treated promptly, it can lead to serious complications.
Compartment Syndrome: A condition where pressure within the muscles builds to dangerous levels, cutting off blood flow and preventing nourishment and oxygen from reaching nerve and muscle cells.

Pulmonary Embolism: While more commonly associated with symptoms like chest pain and shortness of breath, a large pulmonary embolism can lead to decreased cardiac output, resulting in peripheral edema.
Nephrotic Syndrome: A collection of symptoms indicating kidney damage, specifically to the glomeruli, leading to severe swelling, particularly in the legs.
Superficial Thrombophlebitis: Inflammation of the veins just under the skin, which can cause swelling, warmth, and pain in the affected area.
Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain.