The Hip Joint

Anatomy of the Hip Joint

• Type: Ball and socket joint
• **Formed by: **
  • Acetabulum of the pelvis
  • Head of femur
• Acetabulum Labrum:
  • Serves as a shock absorber
  • Increases joint stability by deepening 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: **
  • Connects ilium to femur, located anteriorly
• Ischiofemoral Ligament:
  • Located posteriorly
• Pubofemoral Ligament:
  • Located anteriorly
• Role: All three prevent excessive hip extension
  • Close Pack Position: Full extension
  • Open Pack Position: Flexion

Surface Anatomy

• **Muscle Groups Identification: **
  • Posterior: PSIS, greater trochanter
  • Anterior: ASIS, medial side of knee (sartorius separates quadriceps and hip adductors)

Muscle Groups

• Anterior Compartment (Hip Flexors):
  • Iliacus
  • Psoas Major (joins with iliacus to form Iliopsoas)
  • Sartorius
  • Rectus Femoris (part of quadriceps)
• Posterior Compartment (Hip Extensors):
  • Gluteus Maximus
  • Hamstrings:
    • Medial: Semitendinosus, Semimembranosus
    • Lateral: Biceps Femoris (long head), Biceps Femoris (short head)
• Medial Compartment (Hip Adductors):
  • Pectineus
  • Adductor Longus, Brevis, Magnus
  • Gracilis
• Lateral Compartment (Hip Abductors):
  • Gluteus Medius, Minimus
  • Tensor Fascia Lata (TFL)
  • Iliotibial Band (IT Band)

Deep Hip External Rotators

• **Muscles: **
  • Piriformis
  • Quadratus Femoris
  • Obturator Internus, Externus
  • Gemellus Superior, Inferior

Muscle Functions

• Flexion: Concentrically contracts hip flexors (Iliopsoas, Rectus Femoris, Sartorius)
• Extension: Contract hip extensors (Gluteus Maximus, Hamstrings)
• Abduction/Adduction: Maintain lateral pelvic stability
• External/Internal Rotation:
  • External Rotation (Open Chain): Gluteus Maximus, deep rotators
  • Internal Rotation: Gluteus Minimus, Tensor Fascia Lata, anterior Gluteus Medius

Arthrokinematics

• Flexion/Extension: Primarily spinning
• Abduction/Adduction, Rotation: Rolling and gliding movements

Practical Applications

• Open Chain Movements: Isolated muscle actions (e.g., hip flexion)
• Closed Chain Movements: Muscle actions stabilize pelvis and trunk during activities like walking, standing on one leg, sitting up
• Trunk Movement Control:
  • Hip Flexors (Iliopsoas): Reinforce lumbar curve, anterior pelvic tilt
  • Hip Extensors (Hamstrings): Posterior pelvic tilt, flat lumbar spine, back pain