| | Conditions Treatments | Muscle Strain What muscle flexes thigh and extends leg? The quadriceps muscle, specifically the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius muscles, flex the thigh and extend the leg. Muscle Strain - Related Articles Maternity Care Health Insurance What are Title 42 Federal Government Employees? What does a reproductive system consist of? The Uses of PABA Should you worry if banged your head hard enough to have a contusion? How to Detox With Bentonite When is surfactant produced in the fetus?