() The White House said Thursday that swelling seen on President Donald Trump’s lower legs is from chronic venous insufficiency, adding that the president is still in good health.

What is chronic venous insufficiency?

Chronic venous insufficiency is a common condition, usually affecting those over the age of 50, with the risk of developing it increasing with age. About 1 in 20 adults in the U.S. has chronic venous insufficiency.

The condition happens when veins in the legs don’t allow blood to flow back up to the heart as it normally would. Valves in the veins don’t work properly, causing blood to flow backward and pool in the legs.

Without treatment, chronic venous insufficiency can cause pain, swelling, cramps, varicose veins and leg ulcers. While not a serious health problem, it can be painful and even disabling.

How can you tell if you have chronic venous insufficiency?

Symptoms of chronic venous insufficiency include swelling in the legs and ankles, itchy, painful legs, pain when walking, brown-colored skin, varicose veins, leg ulcers, an urge to move your legs and painful leg cramps or muscle spasms.

Many of those symptoms overlap with other health conditions, so it’s important to check with a doctor if you are experiencing them.

What causes chronic venous insufficiency?

Risk factors for chronic venous insufficiency include being overweight, having a family history or having damage to the leg, including injuries, surgeries and blood clots. Pregnancy can also cause the condition to develop.

It can also be caused by a lack of exercise, high blood pressure, smoking and blood clots in a deep vein in the calf or thigh, a condition known as deep vein thrombosis.

White House Press Secretary Karoline Leavitt said in a briefing the president has no evidence of deep vein thrombosis, which can be fatal.

How is chronic venous insufficiency treated?

Treatment for chronic venous insufficiency can include methods to increase blood flow in the legs, including elevating legs, exercising and wearing compression socks. It may also be treated by medication to increase blood flow or procedures to close problematic veins so blood will flow through other, healthier veins.

The White House did not specify what, if any, treatment Trump is receiving.