Health experts say chronic venous insufficiency is the most common vascular disease in the country. What is it?

Johns Hopkins Medical explained that the condition occurs when the valves in a patient's leg veins don't work well, failing to allow blood to flow back up to the heart. This can cause blood to collect in the legs. Symptoms of the condition can include:

Doctors discuss how common the condition is, why it happens — and whether Trump's symptoms align with his diagnosis.