my baby leg downward from knee is very weak .what should I do for her weak leg.due to weak muscles of leg she doesn't able to stand properly.she always stand on her toes.

A. “Put your baby on his back and gently move his legs up and around, as if he were pedaling a bicycle,” says Dr. Chintapalli. Coo, smile, sing, or make choo-choo or vroom noises while you do the motion. Repeat the movement three to five times, take a break, and then repeat.