Leg swelling generally occurs because of an abnormal accumulation of fluid in the tissues of the lower extremity. The medical term for leg swelling from excessive fluid in the tissues is edema. Persisting indentation of a swollen leg after pressure from a finger is known as pitting edema.
Common causes of leg swelling include salt retention, cellulitis, congestive heart failure, and medication side effects. Less common causes of leg swelling include blood clots in the leg (thrombosis), parasite infection, lymphedema, liver disease, kidney disease, and diseases that cause thickness of the layers of skin, such as scleroderma and eosinophilic fasciitis. In these diseases, the leg swelling is typically characterized by nonpitting edema. When leg swelling occurs for unknown reasons, it is referred to as idiopathic edema.
Symptoms that can be associated with leg swelling include leg pain, numbness, redness, itching, rash, shortness of breath, and ulceration of the skin.