<prompt> Which is an unlocker of knee?Popliteusbiceps femorisSartoriusGastrocnemius  <response>: ANSWER: A PopliteusREF: Grays anatomy 39th ed p. 1465,1482-83 Locking or screw home mechanism: Conjuct medial rotation of femur on tibia in later stages of extension due to quadriceps femoris locks the knee joint.Unlocking of knee joint: At beginning of flexion from full extension with foot flexed, lateral rotation by Popliteus muscle unlocks the joint. 