Lecture on Hip Joint Anatomy and Function

Hip Joint Structure

• Type: Ball and socket joint
• Components: Acetabulum of the pelvic and head of femur
• Acetabulum Labrum: Functions
  • Shock absorber
  • Increases joint stability by increasing the depth of the acetabulum

Degrees of Freedom

• Sagittal Plane: Flexion and extension
• Frontal Plane: Abduction and adduction
• Horizontal/Transverse Plane: Internal and external rotation

Major Ligaments

• Iliofemoral Ligament: Anterior
• Ischiofemoral Ligament: Posterior
• Pubofemoral Ligament: Anterior
• Labrum: Increases joint stability
• Function: Limit hip extension
• Closed Pack Position: Full extension
• Open Pack Position: Flexion

Surface Anatomy

• Posterior: PSIS (Posterior Superior Iliac Spine)
• Side: Greater trochanter
• Landmarks: Head and neck of femur, greater and lesser trochanter
• Muscle Identification:
  • PSIS and greater trochanter: Divide gluteus maximus and gluteus medius
  • ASIS and greater trochanter: Locate tensor fascia lata
  • ASIS to medial knee: Locate sartorius, separates quadriceps and hip adductors

Muscle Groups Acting on the Hip

Anterior Compartment: Hip Flexors

• Iliacus and Psoas Major: Join to form iliopsoas, a major hip flexor
• Sartorius: Originates from ASIS to medial knee
• Rectus Femoris: Part of quadriceps acting on the hip

Posterior Compartment: Hip Extensors

• Gluteus Maximus: Major hip extensor
• Hamstrings:
  • Superficial: Semitendinosus (medial)
  • Deep: Semimembranosus (beneath semitendinosus)
  • Lateral: Biceps femoris (long head and short head)

Medial Compartment: Hip Adductors

• Pectineus
• Adductor Longus
• Adductor Brevis (beneath longus)
• Adductor Magnus (large piece beneath brevis)
• Gracilis (far medial border)

Lateral Compartment: Hip Abductors

• Gluteus Medius
• Gluteus Minimus (beneath gluteus medius)
• Tensor Fascia Lata (TFL)
• IT Band: Connects to TFL, separate from it

Deep Posterior Layer: External Rotators

• Piriformis: Identifies sciatic nerve, beneath gluteus minimus
• Quadratus Femoris: Rectangular-shaped
• Obturator Internus: Middle muscle
• Gemellus Superior: Above obturator internus
• Gemellus Inferior: Below obturator internus
• Obturator Externus: Not visible from the posterior side

Muscle Actions and Movements

Hip Flexion and Extension

• Open Chain Hip Flexion: Concentric contraction of iliopsoas, rectus femoris, sartorius
• Closed Chain Hip Flexion: Involves trunk bending, uses hip flexors concentrically, hip extensors eccentrically
• Hip Flexors: Reinforce lumbar curve, anterior pelvic tilt
• Hip Extensors: Posterior pelvic tilt

Hip Abduction and Adduction

• Function: Maintain lateral stability of pelvis and trunk
• Closed Chain: Gravity pulls pelvis down, opposite hip abductor stabilizes

External and Internal Rotation

• External Rotation: Open chain uses gluteus maximus and deep rotators
• Internal Rotation: Open chain uses gluteus minimus, TFL, anterior fibers of gluteus medius
• Closed Chain External/Internal Rotation: Balance pelvis and trunk over lower extremity