Muscles that Act on the Knee

Question 1

Muscle: Quadriceps
-Rectus femoris
-Vastus medialis
-Vastus lateralis
-Vastus intermedius

Answer 1

Primary Function(s):
Rectus femoris: extends the knee and flexes the hip
All vastus muscles: extend the knee only

Resistance Exercise(s)
Rectus femoris: hanging leg raises, leg extensions, squats
Vastus muscles: leg extensions, squats

Question 2

Muscle: Hamstrings
-Biceps femoris
-Semitendinosus
-Semimembranosus

Answer 2

Primary Function(s):
Biceps femoris: flexes and externally rotates a bent knee
Both “semi” muscles: flex and internally rotate a bent knee

Resistance Exercise(s)
Deadlifts, leg curls

Question 3

Muscle: Popliteus

Answer 3

Primary Function(s):
Flexes and internally rotates a bent knee (tibia)

Resistance Exercise(s):
Leg curls with foot pointing inward

Question 4

Muscle: Gracilis

Answer 4

Primary Function(s):
Flexes the knee

Resistance Exercise(s):
Side-lying bottom leg raises

Question 5

Muscle: Sartorius

Answer 5

Primary Function(s):
Flexes the knee and hip (femur)

Resistance Exercise(s):
Hanging knee-raises with external hip rotation