Quadriceps, Hamstrings & Iliopsoas

Quadriceps Muscle Group

• The quadriceps is a major muscle group located in the anterior thigh that consists of four muscles:

  • Rectus Femoris

    • Origin: Anterior inferior iliac spine (AIIS)

    • Insertion: Patellar tendon to tibial tuberosity

    • Function: Hip flexion and knee extension

  • Vastus Lateralis

    • Origin: Greater trochanter and lateral lip of the linea aspera of the femur

    • Insertion: Combines to form the quadriceps tendon which ends at the patella

    • Function: Knee extension

  • Vastus Medialis

    • Origin: Medial lip of the linea aspera

    • Insertion: Similar to vastus lateralis

    • Function: As for vastus lateralis, with emphasis on patellar alignment (vastus medialis oblique)

  • Vastus Intermedius

    • Origin: Anterior and lateral surfaces of the femoral shaft

    • Insertion: Same as others, but deep to rectus femoris

    • Function: Knee extension

Hamstrings

• The hamstrings are located on the posterior thigh and consist of three main muscles:

  • Biceps Femoris

    • Origin:

      • Long Head: Ischial tuberosity

      • Short Head: Lateral lip of the linea aspera

    • Insertion: Head of the fibula

    • Function: Knee flexion and hip extension, slight lateral rotation of a flexed knee

  • Semitendinosus

    • Origin: Ischial tuberosity

    • Insertion: Proximal medial surface of the tibia (pes anserinus)

    • Function: Knee flexion, hip extension, some medial rotation

  • Semimembranosus

    • Origin: Ischial tuberosity

    • Insertion: Posterior aspect of the medial condyle of the tibia

    • Function: Similar to semitendinosus, also helps with internal rotation

Iliopsoas Group

• The iliopsoas group is critical for hip flexion and comprises:

  • Psoas Major

    • Origin: Transverse processes and bodies of lumbar vertebrae

    • Insertion: Lesser trochanter of the femur

    • Function: Powerful hip flexor, stabilizes the lumbar spine during movement

  • Psoas Minor

    • Origin: Bodies of the lumbar vertebrae (may vary among individuals)

    • Insertion: Iliopubic eminence and pectineal line of pubis

    • Function: Assists with pelvic tilt; of little significance in movement

  • Iliacus

    • Origin: Iliac fossa

    • Insertion: Lesser trochanter

    • Function: Primary hip flexor, plays a minor role in pelvis stability

Key Points of the Hip and Lower Extremity Anatomy

• Innnonimate Bone: Refers collectively to the ilium, ischium, and pubis bones of the pelvis.

• SI Joint: Important for stability and movement between the sacrum and ilium; consists of anterior and posterior ligaments.

• Popliteal Fossa: Area behind the knee where significant vascular and nervous structures are located.

• Acetabulum: Socket of the hip joint where the femur head articulates, surrounded by the acetabular labrum for stability.

Movement Dynamics

• Rectus Femoris: As a two-joint muscle, it acts as a hip flexor and knee extender; critical during activities like running and jumping.

• Hamstrings: Involved in knee flexion; significantly activated during sports that involve sprinting and explosive movements.

• Iliopsoas Group: Key player in activities requiring hip flexion, such as climbing stairs and kicking motions.

Common Injuries and Conditions

• Hamstring Strains: Common in athletes; bleeding and swelling can occur due to the large number of capillaries in the muscle.

• Pelvic and SI Joint Dysfunction: Can lead to lower back pain and issues with mobility; often require special attention in physical therapy.

• Hip Flexor Tightness: Common in individuals with sedentary lifestyles, leading to postural issues and discomfort.