A very simple quad stretch can be performed in most bedrooms. Usually the bed is about knee high and near a wall. The person stands between the bed and the wall, facing the wall. Place the lower leg up on the bed with the hands on the wall for support. That knee will be at about 90 degrees or so. Then you posteriorly tilt the pelvis and slowly extend the torso back till the stretch is felt.
I would incorporate some ROM dynamic movements in their program.
For Your client You may also use “Corrective flexibility”. It uses the principles of autogenic inhibition. It includes self-myofascial release (foam roll) techniques and static stretching.
Self-myofascial release applies gentle pressure on muscle for 20-30 seconds. The force applied stimulates the Golgi tendon organ and creates autogenic inhibition, decreasing muscle spindle excitation.
Static stretching passively takes a muscle to the point of tension and holds it there for 20 seconds, creating autogenic inhibition. Also,contracting the antagonistic muscle during stretch inhibit the muscle being stretched and increasing muscle’s ability to lengthen.
You will have to think in the sagittal plane in order to teach your client this stretch.
As you know the sagittal plan divides the individual in to right and left parts.
With either the right or left part, have your client place (let’s say for the sake of learning the stretch) the right buttocks and thigh on the side of a chair while the left side of the body (the left buttock, thigh,leg are not supported by the chair)
Essentially you are seated on one side of your body.
Take the left leg and extend it behind you with the objective of directing the knee towards the floor. Squeeze the left glute as you perform this exercise and repeat on the opposite side.
You can also perform a stretch for the iliopsoas in this position.
Hope this helps!