Thigh Muscles Diagram, Pictures, List of Actions

The thigh (proximal lower limb) muscles are arranged into three compartments :

• Anterior compartment, also known as the extensor compartment
• Medial compartment, also known as adductor compartment
• Posterior compartment, also known as the flexor compartment

The following diagram illustrates the actions of the terms adduction, abduction, flexion and extension at the different joints. This is important to understand the actions of the thigh muscles in limb movement.

Anterior Compartment Thigh Muscles

This is the largest of the three compartments of the thigh.

Extensors of the Knee

• Muscles
  • Quadriceps femoris
  • Rectus femoris
  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius
• Actions
  • Extension of the leg at the knee joint
  • Steadies the hip joint and assists the iliopsoas muscle with flexion of the thigh (rectus femoris muscle)

Flexors of the Hip

• Muscle
  • Pectinues
• Actions
  • Adduction and flexion of the thigh
  • Assists with medial rotation of the thigh

• Muscles
  • Iliopsoas (psoas major, psoas minor, iliacus)
• Actions
  • Flexion of the thigh at the hip joint
  • Stabilizing the hip joint

• Muscle
  • Sartorius
• Actions
  • Abducts and flexes thigh at the hip joint
  • Laterally rotates the the thigh at the hip joint
  • Flexes leg at knee
  • Medially rotates leg when flexed

Medial Compartment Thigh Muscles

Adductors of the Thigh

• Muscle
  • Adductor longus
• Action
  • Adducts the thigh

• Muscle
  • Adductor brevis
• Actions
  • Adducts the thigh
  • Assists with flexion of the thigh

• Muscle
  • Adductor magnus
• Actions
  • Adducts the thigh
  • Extension of the thigh (hamstring)
  • Flexion of the thigh (adductor)

• Muscle
  • Gracilis
• Actions
  • Adduction of the thigh
  • Flexion of the leg
  • Assist with medial rotation of the leg

• Muscle
  • Obturator externa
• Action
  • Lateral rotation of the thigh
  • Stabilizes head of the femur

Posterior Compartment Thigh Muscles

The muscles below are collectively known as the hamstring muscles.

Extensors of the Hip

• Muscles
  • Semitendinosus
  • Semimembranous
• Actions
  • Extension of the thigh
  • Flexion of the leg
  • Medial rotation of the leg when the knee is flexed
  • Extension of the trunk when the thigh and leg is flexed

Flexion of the Knee

• Muscle
  • Biceps femoris
• Actions
  • Flexion of the leg
  • Lateral rotation of the leg when the knee is flexed
  • Extension of the thigh