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. 

Generally  it is related to reflux of the GSV with tributary or excessery vein component. You need a proper evaluation with ultrasound . 

Hi Shelly Cameron, 
Varicose veins are very commonly located in the calves, behind the knees and thighs. The cause is usually an underlying vein valve leak (venous insufficiency). An ultrasound is highly recommended prior to treatment as in a small segment, varicose veins may represent an underlying clot in the deep vein system which needs to be addressed immediately. 
In a nutshell, an ultrasound of both legs including the deep system followed by a treatment plan. If you do not have any symptoms of venous insufficiency, a cosmetic route for treatment is your option. Non-surgical methods include ultrasound guided sclerotherapy. 

Most likely, tributary varicose veins behind the knee originate from the small saphenous system. Less commonly, they originate from the intersaphenous system that connects the great and lesser saphenous systems. You need a venous Doppler Ultrasound exam (Duplex scan) to measure the veins, map the entire saphenous system (great and lesser) and also determine if you have venous insufficiency. In the interim, wear graduated medical compression stockings that are thigh high to help relieve symptoms. I recommend durable, microfiber 20-30 mm Hg medical grade compression stockings from VenaSmart. 

If you have bilging veins behind your knee, you may need an ultrasound.  We usually recommend a venous insufficiency study to see if there is reflux in the veins and what is causing the veins to be varicosed. 

These are most likely varicose veins.  The first step is to seek attention from a vein specialist who can evaluate your legs and most likely perform an ultrasound.  Once the ultrasound is done, that doctor can assist you in finding the most appropriate treatment.

Bulging veins which often times look like grapes are called varicose veins and these are due to malfunctioning (refluxing) valves of usually the saphenous system of veins.  The refluxing valves can be caused by trauma but most commonly are due to genetics.  These can be easily treated by a closure procedure.  See a vein specialist for a full venous ultrasound to determine the cause of the problem and help to plan a treatment.