Bulging veins behind my knee. What is the cause?

What you are describing sounds like varicose veins.  They are sometimes caused by an underlying condition called venous reflux.  It is often genetic and can also be caused by prolonged standing, pregnancy, weight and other factors.  The evaluation requires a doppler ultrasound test that is painless, without risk and can be performed by a vascular surgeon or other vein specialist. 

I would start with a transilluminating light examination followed by ultrasound to diagnose and treat the source of your varicose veins. Most of these procedures are performed in an outpatient setting. Best, Dr. KaramanoukianLos Angeles

Venous insufficiency could be causing the veins behind your knee. Venous insufficiency happens when the valves that maintain blood flowing out of the legs and back to the heart no longer function. This causes the blood to pool in the legs and one of the signs is bulging veins among other signs and symptoms. Venous insufficiency is considered a medical condition with risk factors like age, gender, family history, heavy lifting, multiple pregnancies, obesity, standing for long time etc.  First thing to consider is a visit to vein specialist so your legs can be examined. A lower extremity venous ultrasound can confirm if an underlying venous insufficiency is causing these bulging veins behind your knee. This way the specialist can manage your care and options to treatment.