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Edema (leg swelling)


Edema (leg swelling) may affect both legs equally or may be more of a problem in one leg. The causes of swelling in one leg may be similar to the other, but it is not unusual for different factors to cause swelling in each. Frequently, more than one factor may cause leg swelling, such as venous insufficiency, obesity and previous saphenous vein harvest for heart bypass surgery.

Vein pressure conditions

Swelling may occur due to high pressure in leg veins, local injury, inflammatory changes, obstruction of lymphatic fluid outflow, infection, low blood protein levels, obesity, pregnancy, fluid retention states or drug effects. High leg vein pressure results in fluid, proteins and blood cells leaking through the wall of small veins into the soft tissues, especially near the ankles. This causes pitting edema, a swelling that will leave a temporary indentation in the skin with pressure from a shoe, sock or intentional pressure such as a finger squeeze. Some of the causes of leg edema due to elevated venous pressures include:

  • Venous insufficiency, a failure of one-way valves in the veins
  • Obesity, which increases the pressures on veins and lymphatic channels in the abdomen and pelvis resulting in a partial obstruction of venous and lymphatic outflow from the legs back to the heart
  • Deep vein thrombosis, clots obstructing venous flow back to the heart
  • Post-phlebitic syndrome, chronic obstruction of leg or pelvis veins due to previous deep vein thrombosis
  • Pelvic vein compression due to an overlying artery, organ or tumor
  • Failure of the calf muscles to pump venous blood out of the legs due to stroke, venous injury, arthritis limiting ankle motion or inactivity

Traumatic conditions

Localized swelling may be due to trauma, hematoma (collection of non-flowing blood in the soft tissue), infections, fracture, superficial thrombophlebitis (clots in veins of the fatty tissues), rupture of a tendon or muscle, cyst at a joint (such as a synovial cyst at the knee) and sometimes spontaneous bleeding into the tissue due to a ruptured blood vessel.

Chronic conditions

Chronic leg swelling may also be due to states that result in generalized body fluid expansion. This may be more apparent in the legs due to the effect of gravity, such as:

  • Congestive or ischemic heart failure
  • Pulmonary hypertension
  • Pericarditis, which limits heart pumping function
  • Pregnancy
  • Idiopathic edema, often involving both upper and lower extremities in premenopausal women
  • Liver disorders
  • Kidney disorders
  • Hypothyroidism
  • Low protein states such as malnutrition, protein loss due to illness, kidney or intestinal diseases
  • Medication


Some of the most common medications that cause leg swelling are non-steroidal anti-inflammatory drugs taken for pain relief or for arthritic discomfort, and calcium channel blockers taken for heart disease or hypertension. Some of the more common drugs that may cause swelling include:

  • Antihypertensive drugs
    • Calcium channel blockers
    • Beta blockers
    • Clonidine
    • Hydralazine
    • Methyl dopa
    • Minoxidil
  • Nonsteroidal anti-inflammatory drugs
    • Ibuprofen, Naproxen, and many others in this class
  • Hormones
    • Estrogen, progesterone, testosterone.

Other causes

Cellulitis – infection of the skin and fatty leg tissues – may cause swelling with pain and tenderness. Pain from cellulitis may be very severe or may manifest as tenderness and mild pain with faintly pink to bright red skin.

Swelling of the foot, especially if the skin does not pit with brief application of pressure, may be due to lymphedema, a failure of the microscopic channels that move tissue fluid from the extremity back to the blood stream at the upper chest. Some of the causes of lymphedema include:

  • Congenital—present at birth
  • Acquired– due to recurrent infection or obstruction
    • Post-surgical—excision of vein for vein grafts, lymph node dissection for tumor
    • Malignancy—lymphoma or other diseases affecting the lymph nodes
    • Obesity—due to compression of lymphatic channels in the abdomen or pelvis

After venous insufficiency, obesity is the next most common cause of lower extremity swelling in the United States. Abdominal obesity partially obstructs venous outflow and lymphatic outflow from the legs. Obesity also accelerates the stretching of the leg veins due to the effects of gravity, thus contributing to the progression of venous insufficiency.