See A-Z of rehabilitation exercises
This is an exercise to stretch the quads muscle.
Remember that stretches need to be done slowly and held for a few seconds to obtain the full benefit,
In case you cannot see the video, here is a still sequence -
Lean lightly against a wall or a table with the leg bent to 90 degrees and the foot resting on a chair placed behind you.
Slowly bend at the hips and lower your body until you can feel your quads taking the stretch. The shoulder, hip and heel should be in a straight line. Hold this position for 10 seconds.
Stand up again, and repeat 5 times.