Lower Body Skeletal Muscles

Iliacus

  • Origin: Iliac fossa of the pelvis.

  • Insertion: Lesser trochanter of the femur.

  • Functions:

    • Hip flexion, adduction, and external rotation of the hip.

    • When the femur is fixed, it assists in flexion of the lumbar spine.

Psoas Major

  • Origin: Transverse processes of L1-L5 and intervertebral discs of T12.

  • Insertion: Lesser trochanter of the femur.

  • Functions:

    • Hip flexion, adduction and external rotation of the hip.

    • Rotation of the lumbar spine.

Gluteus Maximus

  • Origin: Posterior aspects of ilium, sacrum, and coccyx.

  • Insertion: Merges with the tensor fasciae latae to form the iliotibial band.

  • Functions:

    • Extends and externally rotates the hip.

    • ABDuction and ADDuction of the hip.

Biceps Femoris

  • Origin: Ischial tuberosity.

  • Insertion: Head of the fibula and lateral tibial condyle.

  • Functions:

    • Hip extension.

    • Flexion of the knee.

Semitendinosus

  • Origin: Ischial tuberosity.

  • Insertion: Inferior to medial tibial condyle.

  • Functions:

    • Hip extension.

    • Flexion of the knee.

Semimembranosus (Deep to Semitendinosus)

  • Origin: Ischial tuberosity.

  • Insertion: Medial tibial condyle.

  • Functions:

    • Hip extension.

    • Flexion of the knee.

    • Assists with internal rotation and adduction of the hip.

Quadriceps Femoris Group

  • Rectus Femoris:

    • Origin: Anterior inferior iliac spine.

    • Insertion: Tibial tuberosity.

    • Function: Hip flexion and weak abduction.

  • Vastus Lateralis:

    • Origin: Greater trochanter.

    • Insertion: Lateral patella, anteriolateral tibial condyle, rectus femoris tendon.

    • Function: Extension of the knee.

  • Vastus Intermedius: (Deep to rectus femoris)

    • Origin: Proximal 2/3 of anterior femur.

    • Insertion: Inferior aspect of patella and tendons of vastus lateralis and medialis.

    • Function: Extension of the knee.

    Vastus Medialis:

    • Origin: Intertrochanteric line and linea aspera.

    • Insertion: Medial tibial condyle, medial patella, and medial aspect of rectus femoris tendon.

    • Function: Extension of the knee.

Gracilis

  • Origin: Anterior inferior aspect of pubic symphysis and inferior pubic bone.

  • Insertion: Distal to medial tibial condyle.

  • Functions:

    • Adduction, flexion, and external rotation of the hip.

    • Knee flexion and internal rotation of the tibiofibular joint.

Gastrocnemius

  • Origin: Posterior aspects of lateral and medial condyles of the femur.

  • Insertion: Calcaneus.

  • Functions:

    • Plantar flexion of the ankle.

    • Flexion of the knee.