parenting problem. check the hierarchy in the outliner. the upper leg bone is loose. the upper leg mesh group is not translated and as loose. you also gotta parent correct or skip/fix the double knee joint. and the upper leg uses the same texture as the waist. :)

it's rather easy, just go into edit mode and grab the two bones, and then parent the "hip" or upperleg bone to the lowerleg bone or "knee"