On Thursday, the White House announced that US President Donald Trump has a medical condition in his veins called chronic venous insufficiency.

During a regular news briefing, Press Secretary Karoline Leavitt revealed that Trump, 79, had noticed swelling in his legs, prompting a check-up with his doctor who diagnosed him with the condition.

Trump had also been recently photographed with patches of make-up on the back of his hand. The White House has said it is unrelated to the vein condition but is instead bruising as a result of frequent handshaking.

Here are the some of the key things to know about the US president's diagnosis.

Trump's condition is "benign and common", particularly in individuals over the age of 70, according to a note from White House physician, Captain Sean Barbabella, released to reporters.

Chronic venous insufficiency occurs when leg veins don't allow blood to flow back up to the heart, causing it to pool in the lower limbs.

Normal blood flow from the legs back up to the heart moves against gravity, which in older people can become a difficult process.

This can be due to weakening valves in veins, something that can occur as people age.

When blood pools in the legs due to chronic venous insufficiency, it can cause swelling like the kind seen in Trump's ankles in recent photographs.

It can also involve pain and itching, or in more serious cases can present with changes to the skin, ulcers, bleeding or deep vein thrombosis - which is blood clotting in the leg.

"It can be associated with serious conditions, but in and of itself it is not a serious condition, and one that is very common," Dr Matthew Edwards, chair of the Department of Vascular Surgery at Wake Forest University, told the BBC.

"People in his age (group), I would say probably somewhere between 10 and 35% of people would have this."

Experts say other risks include being overweight, having a history of blood clots, and having jobs that require patients to be on their feet for long durations.

After noticing swelling in his legs, President Trump was evaluated by the White House Medical Unit "out of an abundance of caution", a statement from Trump's doctor, Sean Barbabella, said.

Dr Barbabella wrote that President Trump underwent a "comprehensive examination" that revealed chronic venous insufficiency, which he says is a "benign and common condition".

"Importantly, there was no evidence of deep vein thrombosis (DVT) or arterial disease," he said, and added that Trump "remains in excellent health".

Tests also showed "normal cardiac structure and function," Dr Barbabella said, adding: "No signs of heart failure, renal impairment, or systemic illness were identified."

Dr Barbabella also noted bruising on the back of Trump's hand, which has been noticed in recent photographs, sometimes covered by make-up.

"This is consistent with minor soft tissue irritation from frequent handshaking and the use of aspirin, which is taken as part of a standard cardiovascular prevention regimen," he said.

Prof Ian Chetter, president of the Vascular Society of Great Britain and Ireland, told the BBC that this is possible.

The US-based Society for Vascular Surgery said the condition can cause heaviness in the affected limb, as well as swelling and pain.

In some cases, chronic venous insufficiency can also cause painful cramps, spasms and leg ulcers.

It can also lead to reduced mobility and physical activities, Prof Chetter said.

Wearing custom-made, medical-grade compression stockings can help manage the condition, and experts also recommend patients elevating their legs at night and using lotion.

The condition is "very, very rarely life threatening", Prof Chetter said.

In April, Trump underwent his first annual physical of his second presidential term.

"President Trump remains in excellent health, exhibiting robust cardiac, pulmonary, neurological, and general physical function," Dr Barbabella said in a memo at the time.

That health assessment revealed that the president takes several medications to control his cholesterol - Rosuvastatin and Ezetimibe, as well as Aspirin for cardiac prevention and Mometasone cream for a skin condition.

The US president has regularly touted his good health and once described himself as "the healthiest president that's ever lived".

After his first annual physical, Trump told reporters that "overall, I felt I was in very good shape", and added that he thought he had "a good heart, a good soul, a very good soul".