You want to stretch your quadriceps without standing or kneeling. What should you do?
To stretch your left quadricep lie on your left side. With your right hand, pull the top of your left foot toward your butt with your knee bent.
To stretch your right quadricep lie on your right side. With your left hand, pull the top of your right foot toward your butt with your knee bent.
See "Side lying quad stretch" here on Glamour.com (the #4 item in the article).