Why do our legs swell in a plane?

Why do our legs swell in a plane? Who do my feet swell during a flight?

Many of us have notice that after a long flight, or after travelling for hours in a train or a bus, our feet and lower legs swell and become painfull. This is a normal phenomenon.

It can also occur after prolonged periods of standing. This condition is called : dependant edema. The pressure (the hydrostatic pressure) becomes high in the legs after standing for a long time or in an airplane by the effect of gravity. So fluids are shifted outside the blood vessels to the tissues producing this swelling (oedema). The swelling may press on nerve endings producing pain.

It's called dependant because it depends on the position and gravity. So if you stand for along time it collects in your feet. In patients who are bed-ridden it may accumulate around the sacrum and in the back.

This is normal in the situations mentioned above and in pregnancy, it's also more common in old age. But in some diseases, dependant edema is a sign of the disease, as in liver failure and heart failure. If the edema is only in one leg, it's suggestive of deep vein thrombosis.

Related:

Foot, leg, and ankle swelling.