Anatomy Muscles of Lower Limb 5c0f299d Chief Extensor at knee joint is A Biceps femoris B Quadriceps femoris C Semitendinosus D Semimembranosus High-Yield Explanation Quadriceps femoris is knee Extensor. Hamstrings (Biceps femoris long head, Semitendinosus, Semimembranosus and Adductor magnus) are Knee Flexors.