What are some causes of swelling of the legs?

Many things: Varicose veins with chronic venous insufficiency, superficial thrombophlebitis, deep venous thrombosis, lymphedema, knee, hip, and/or ankle arthritis that prevents normal ambulation, obesity, prolonged standing, liver or kidney trouble, hypothyroidism, abnormal protein levels, all kinds of heart conditions that cause heart failure, the list is long and this doesn't cover everything by any means.

Water and gravity: Our bodies have a large amount of water needed to keep organs functioning. The vessels that carry the fluids are not perfect and they can leak. Also, our tissues have a certain amount of water to stay moist and pliable. Gravity works to pull the fluids down towards the feet even in healthy people. It will worsen as the day progresses. Treatment is compression socks/elevation. Avoid water pills.

Many causes: One of the most common cause of leg swelling is lymphedema. This is caused by poor lymphatic circulation. Venous insufficiency primarily from superficial or deep vein failure can also cause leg swelling. Some medications can cause swelling. Other less likely cause are heart failure, cirrhosis of the liver and kidney problems. I recommend you get checked out by a doctor if you have leg swelling.

Leg swelling.: There are many reasons to have leg swelling and it can involve one or both legs. This swelling can be due to underlying medical problems such as heart, lung, liver or kidney disease or it could be due to other problems such as lymphedema, venous insufficiency or venous clots. Infections and trauma can also lead to leg swelling. If you have swelling you should start with a leg venous ultrasound.