On a limited budget it's somewhat hard to animate someone running without it looking jerky. As recently as The Perils of Penelope Pitstop, animators tended to draw legs moving with very little bending of the knee, sometimes at even a full run. In real life, this would be more than a little painful, as shown in this animated insert from Sesame Street. Some artists go (stop?) an extra step if a character has a skirt. The legs might be drawn nearly straight all the way down even while stationary, as if she doesn't have knees, thighs, or defined hips. See also Wheel-O-Feet.