when your leg falls asleep.what causes it? why does it hurt when the feeling returns?

Question

Please answer in lay terms as specific as possible

Answer 1

Since this sensation almost always occurs when one is sitting on or crossing one's legs, it happens because the nerves are being compressed and the connections which send the sensations of feeling are temporarily cut off.

Once one no longer applies such compression, the feeling comes back as the connections are made again.

Answer 2

When you cut off normal circulation to your extremedies, they fall asleep. When you release the pressure and circulation returns to normal, blood floods back into your capilaries which can feel like pins and needles.