Hi,
I found this site using Stumble Upon ...I just wanted to mentionthat the name of this exercise is incorrect.
Though I realise that the target audience may not have studied anatomy, kinetics or resistance training much, however, I feel it nessessary to point out that abduction is a movement away from the mid-line of the body. In this way it is infact impossible to abduct or adduct any part of the 'butt'. Hip Extention or Butt Raises may be more suitable names.

Picture does not match the text!

@Jamie, The person is to abduct their knee - the title is incorrect with using 'butt', but you are still abducting a body part, and the butt muscle group is being used to abduct the knee.

That's the same pic from butt raise. It sounds like you're in a sitting position, while laying on your side, with the arm from whatever side you're laying on stretched above your head. You touch your feet together, and open up your legs/knees like you have a ball between them or something while maintaining contact (with your feet)... so.. if that helps create a better mental picture, you're welcome. Lol.