Muscles - Thigh (Anterior Compartment)

Question 1

What nerve innervates the muscles of the anterior compartment?

Answer 1

Femoral nerve (L2-L4)

Question 2

What is the function of these muscles?

Answer 2

Extension of the leg at the knee joint.

Question 3

What are the muscles of the anterior compartment?

Answer 3

1) Quadratus femoris
2) Pectineus
3) Sartorius

Iliopsoas passes into the anterior compartment also.

Question 4

Iliopsoas

Answer 4

There are two muscles that make up the iliopsoas: the iliacus and psoas major muscles.

Origin (psoas major) - lumbar vertebrae

Origin (iliacus) - iliac fossa of pelvis

Insertion - lesser trochanter of femur.

Innervation (psoas major) - anterior rami of L1-L3

Innervation (iliacus) - femoral nerve

Action - It does not extend at the knee. It flexes the thigh at the hip joint.

Question 5

Quadriceps femoris

Answer 5

Made up of four muscles: vastus lateralis, intermedius and medialis, and rectus femoris.

They insert distally to the patella via the quadriceps tendon.

Vastus lateralis

Origin - greater trochanter and lateral lip of linea aspera

Actions - extends the at the knee joint and stabilises the patella.

Innervation - femoral nerve

Vastus intermedius

Origin - Anterior and lateral surfaces of the femoral shaft

Actions - extends at the knee and the stabilises the patella.

Innervation - femoral nerve

Vastus medialis

Origin - intertrochanteric line and medial lip of the linea aspera

Actions - extends at the knee and stabilises the patella, particularly due to the horizontal fibres at the distal end.

Innervation - femoral nerve

Rectus femoris

Origin - AIIS and just above the acetabulum. Runs straight down the leg

Insertion - attaches to the patella via the quadratus femoris tendon.

Action - Flexes at the thigh and extends at the knee joint.

Innervation - femoral nerve

Question 6

Sartorius

Answer 6

Longest muscle in the body. Runs inferomedially. More superficial than other muscles.

Origin - ASIS

Insertion - super and medial surface of tibia

Innervation - femoral nerve

Actions -

at the hip joint - flexor, abductor and lateral rotator.

at the knee joint - flexor

Question 7

Pectineus

Answer 7

Forms the base of the femoral triangle. Dual innervation. Runs between the anterior and medial compartments.

Origin - pectineal line of the surface of the pelvis.

Insertion - pectineal line of the posterior side of the femur, just inferior to the lesser trochanter.

Innervation - Femoral nerve and a maybe a branch of the obturator nerve.

Action - Adduction and flexion at the hip joint.

Question 8

Clinical relevance - testing the quadratus femoris

Answer 8

Used to test the femoral nerve is case of palsy.

Patient is presented supine and the leg slightly flexed. Patient is asked to extend their leg against resistance.

If femoral nerve is damaged, muscle will fail to contract.