11.6 Appendicular Muscles of the Pelvic Girdle and Lower Limbs

The pelvic girdle and thigh muscles play crucial roles in hip and leg movement. From the powerful gluteus maximus to the adductor group, these muscles enable walking, running, and other lower body actions. They work together to flex, extend, abduct, and rotate the thigh.

Leg and foot muscles control ankle and toe movements. Divided into anterior, lateral, and posterior compartments, they enable actions like dorsiflexion, plantarflexion, and toe flexion. Understanding these muscles is key to grasping lower limb function and mobility.

Muscles of the Pelvic Girdle and Thigh

Muscles of pelvic girdle and lower limb

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• Iliopsoas consists of two muscles that flex the hip joint (psoas major and iliacus)
  • Psoas major originates from the transverse processes and bodies of lumbar vertebrae and inserts on the lesser trochanter of femur
  • Iliacus originates from the iliac fossa and inserts on the lesser trochanter of femur
• Gluteus maximus is the largest muscle of the buttocks originates from the ilium, sacrum, and coccyx and inserts on the gluteal tuberosity of femur and iliotibial tract
• Gluteus medius originates from the ilium and inserts on the greater trochanter of femur abducts and medially rotates the thigh
• Gluteus minimus originates from the ilium and inserts on the greater trochanter of femur abducts and medially rotates the thigh
• Tensor fasciae latae originates from the iliac crest and inserts on the iliotibial tract flexes, abducts, and medially rotates the thigh
• Adductor longus originates from the pubic body and inserts on the linea aspera of femur adducts and medially rotates the thigh
• Adductor brevis originates from the pubic body and inserts on the linea aspera of femur adducts and medially rotates the thigh
• Adductor magnus originates from the pubic ramus and ischial tuberosity and inserts on the linea aspera and adductor tubercle of femur adducts and medially rotates the thigh
• Gracilis originates from the pubic body and inserts on the medial surface of proximal tibia adducts the thigh and flexes the knee
• Pectineus originates from the pectineal line of pubis and inserts on the pectineal line of femur adducts and flexes the thigh

Actions of thigh, leg, and foot muscles

• Thigh muscles
  • Quadriceps femoris consists of four muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) that extend the knee joint
  • Hamstrings consist of three muscles (biceps femoris, semitendinosus, semimembranosus) that flex the knee and extend the hip
  • Adductors consist of five muscles (adductor longus, adductor brevis, adductor magnus, pectineus, gracilis) that adduct the thigh
• Leg muscles
  • Anterior compartment contains muscles (tibialis anterior, extensor digitorum longus, extensor hallucis longus) that dorsiflex and invert the foot and extend the toes
  • Lateral compartment contains muscles (fibularis longus and fibularis brevis) that evert and plantarflex the foot
  • Posterior compartment
    • Superficial muscles (gastrocnemius and soleus forming the triceps surae) plantarflex the foot
    • Deep muscles (tibialis posterior, flexor digitorum longus, flexor hallucis longus) plantarflex and invert the foot and flex the toes
• Foot muscles
  • Intrinsic muscles enable fine movements of the toes and support the arches of the foot

Compartments in thigh and leg

• Thigh compartments
  • Anterior compartment contains the quadriceps femoris and primarily extends the knee
  • Medial compartment contains the adductor muscles and pectineus and primarily adducts the thigh
  • Posterior compartment contains the hamstrings and primarily flexes the knee and extends the hip
• Leg compartments
  • Anterior compartment contains muscles that dorsiflex and invert the foot and extend the toes (tibialis anterior, extensor digitorum longus, extensor hallucis longus)
  • Lateral compartment contains muscles that evert and plantarflex the foot (fibularis longus, fibularis brevis)
  • Posterior compartment
    • Superficial muscles plantarflex the foot (gastrocnemius, soleus)
    • Deep muscles plantarflex and invert the foot and flex the toes (tibialis posterior, flexor digitorum longus, flexor hallucis longus)

Muscle Function and Interaction

• Origin and insertion points determine the muscle's action and range of motion
• Innervation by specific nerves controls muscle contraction and function
• Antagonist muscles work in opposition to produce smooth, controlled movements
• Synergist muscles work together to assist the primary mover in an action
• Muscle fiber types (slow-twitch and fast-twitch) influence endurance and power output
• Biomechanics principles explain how muscles generate force and movement across joints

Muscles of the Leg and Foot

Muscles of pelvic girdle and lower limb

• Tibialis anterior originates from the lateral condyle and upper 2/3 of lateral surface of tibia and inserts on the medial cuneiform and base of 1st metatarsal dorsiflexes and inverts the foot
• Extensor digitorum longus originates from the lateral condyle of tibia and upper 3/4 of anterior surface of fibula and inserts on the middle and distal phalanges of toes 2-5 extends the toes
• Extensor hallucis longus originates from the middle 1/3 of anterior surface of fibula and interosseous membrane and inserts on the distal phalanx of great toe extends the great toe
• Fibularis longus originates from the head and upper 2/3 of lateral surface of fibula and inserts on the plantar surface of medial cuneiform and base of 1st metatarsal everts and plantarflexes the foot
• Fibularis brevis originates from the lower 2/3 of lateral surface of fibula and inserts on the tuberosity on lateral side of base of 5th metatarsal everts and plantarflexes the foot
• Gastrocnemius has two heads of origin (medial head from posterior surface of medial femoral condyle, lateral head from posterior surface of lateral femoral condyle) and inserts on the posterior surface of calcaneus via calcaneal tendon plantarflexes the foot
• Soleus originates from the posterior surface of head and upper 1/3 of fibula and soleal line of tibia and inserts on the posterior surface of calcaneus via calcaneal tendon plantarflexes the foot
• Tibialis posterior originates from the posterior surface of interosseous membrane and adjacent surfaces of tibia and fibula and inserts on the tuberosity of navicular, cuneiforms, cuboid, and bases of metatarsals 2-4 plantarflexes and inverts the foot
• Flexor digitorum longus originates from the posterior surface of tibia below soleal line and inserts on the plantar surface of bases of distal phalanges of toes 2-5 flexes the toes
• Flexor hallucis longus originates from the lower 2/3 of posterior surface of fibula and inserts on the plantar surface of base of distal phalanx of great toe flexes the great toe