Lower Limb Muscles: Anatomy and Function

Posted on Mar 4, 2025 in Human Biology

Gluteal Muscles

  • Gluteus Maximus:
    • Origin: Upper coccyx, sacrum, and posterior ilium.
    • Insertion: Posterior femur.
    • Action: Extension and external rotation of the thigh; helps maintain an upright posture. The sciatic nerve passes beneath it.
  • Gluteus Medius:
    • Origin: Middle coccyx.
    • Insertion: Greater trochanter of the femur.
    • Action: Abduction and internal rotation of the thigh.
  • Gluteus Minimus:
    • Origin: Iliac crest.
    • Insertion: Greater trochanter of the femur.
    • Action: Abduction and internal rotation of the thigh.
  • Piriformis:
    • Origin: Anterior sacrum.
    • Insertion: Greater trochanter.
    • Action: External rotation of the thigh.

Anterior Thigh Muscles

  • Sartorius: (The longest muscle in the body)
    • Origin: Anterosuperior iliac spine.
    • Insertion: Medial surface of the proximal tibia (crosses the thigh diagonally).
    • Action: Flexion, abduction, and lateral rotation of the thigh.
  • Quadriceps Femoris: (Largest muscle group in the body)
    • Rectus Femoris:
      • Origin: Anteroinferior iliac spine.
    • Vastus Lateralis:
      • Origin: Lateral surface of the femur.
    • Vastus Medialis:
      • Origin: Medial surface of the femur.
    • Vastus Intermedius:
      • Origin: Diaphysis of the femur.
    • Common Insertion: All four heads converge into the patellar tendon, inserting into the tibial tuberosity.
    • Action: Knee extension and assists in hip flexion.

Medial Thigh Muscles (Adductors)

  • Adductor Magnus:
    • Origin: Inferior pubic ramus, ischial ramus, and ischial tuberosity.
    • Insertion: Linea aspera of the femur and adductor tubercle of the femur.
    • Action: Adduction and flexion of the thigh.
  • Adductor Brevis:
    • Origin: Body of the pubis.
    • Insertion: Upper part of the linea aspera of the femur.
    • Action: Adduction and flexion of the thigh.
  • Adductor Longus:
    • Origin: Pubic crest and pubic symphysis.
    • Insertion: Linea aspera of the femur.
    • Action: Adduction of the thigh.

Posterior Thigh Muscles (Hamstrings)

These muscles share a common origin on the ischial tuberosity.

  • Biceps Femoris:
    • Origin: Long head from the ischial tuberosity, short head from the linea aspera of the femur.
    • Insertion: Head of the fibula.
    • Action: Flexion of the leg and extension of the thigh.
  • Semitendinosus:
    • Origin: Ischial tuberosity.
    • Insertion: Posterior medial tibial condyle.
    • Action: Flexion of the leg and extension of the thigh.
  • Semimembranosus:
    • Origin: Ischial tuberosity.
    • Insertion: Posterior part of the tibial condyle.
    • Action: Flexion of the leg and extension of the thigh.

Leg Muscles

Anterior Compartment

  • Tibialis Anterior:
    • Origin: Lateral condyle and proximal shaft of the tibia.
    • Insertion: Medial cuneiform and first metatarsal.
    • Action: Dorsiflexion, abduction, and internal rotation of the foot.
  • Extensor Hallucis Longus:
    • Origin: Anterior surface of the fibula.
    • Insertion: Distal phalanx of the great toe (hallux).
    • Action: Extension of the great toe.
  • Extensor Digitorum Longus:
    • Origin: Lateral tibial condyle and proximal fibula.
    • Insertion: Distal phalanges of the lateral four toes.
    • Action: Extension of the lateral four toes.

Lateral Compartment

  • Peroneus Longus (Fibularis Longus):
    • Origin: Proximal two-thirds of the fibula.
    • Insertion: Tendon passes behind the lateral malleolus, crosses the sole of the foot, and inserts into the first metatarsal and medial cuneiform.
    • Action: Abduction and plantar flexion of the foot.

Posterior Compartment (Deep)

  • Flexor Digitorum Longus:
    • Origin: Posterior surface of the tibia.
    • Insertion: Tendon passes behind the medial malleolus and inserts into the bases of the distal phalanges of the lateral four toes.
    • Action: Flexion of the lateral four toes.
  • Flexor Hallucis Longus:
    • Origin: Posterior surface of the fibula.
    • Insertion: Tendon passes behind the medial malleolus and inserts into the base of the distal phalanx of the great toe.
    • Action: Flexion of the great toe.
  • Triceps Surae (Superficial): Consists of the gastrocnemius and soleus.
    • Gastrocnemius: The more superficial muscle with two heads originating from the medial and lateral femoral condyles.
    • Soleus: Originates from the proximal third of the fibula and tibia.
    • Common Insertion: Both muscles converge and insert into the calcaneus via the Achilles tendon.
    • Action: Plantar flexion of the foot (raising the heel).
  • Plantaris:
    • Origin: Calcaneus.
    • Insertion: Four tendons that insert to the middle phalanges.
    • Action: Weak plantar flexion and flexion of the toes.