Assisted knee extension with hip at 90 degrees in supine - with ankle dorsiflexion

You will require someone to assist you with the exercise.
Lie on your back.
Your assistant should support on top of your foot and knee and bend your hip so that it is at a right angle.
Keeping your hip bent upwards, your assistant will straighten your knee and push your foot towards your knee, hold the position then return to the start position.
Join in with the movement as much as possible.