anatomy of the hip joint

• The pelvic girdle

  2 hip (innominate) bones joined at the sacrum posteriorly

  Functions:

  • Supports body weight
  • Site for muscle attachment
  • Supports and protects the pelvic organs
  • Provides bony support for the birth canal
• innominate

  Consists of 3 bones fused together:

  • Ilium 
  • Pubis
  • Ischium

  Fusion of the 3 bones in the acetabulum occurs between 16 and 18 years
• Pubic symphysis

  • Cartilaginous joints between the medial surfaces of the bodies of the 2 pubic bones 
  • Fibrocartilaginous interpubic disc
  • Above, below and in front of the joint thickenings of fibrous tissue form ligaments
  • Normally no movement between the bones involved (small degree of movement occurs during pregnancy)
• the pelvis during pregnancy

  • The hormone relaxin and progesterone relax muscles and loosen ligaments and joints (especially in the pelvic area)
  • Relaxin levels are at their highest in the first trimester
  • 10-15% increase in diameter (pelvic outlet) facilitates childbirth
  • Relaxin will remain in the body for up to 5 months
• What type of joint is the sacroiliac joint (SIJ)?

  Synovial joint
• What forms the sacroiliac joint?

  The auricular surface of the ilium and the ala of the sacrum
• What surrounds the sacroiliac joint?

  A fibrous capsule
• Why is only a small movement possible in the sacroiliac joint?

  Due to the arrangement of the joint surfaces and ligamentous support
• What are the main ligaments associated with the sacroiliac joint?

  • Anterior sacroiliac ligament
  • Posterior sacroiliac ligaments
  • Interosseous sacroiliac ligament
  • Long and short posterior sacroiliac ligaments
  • Sacrospinous ligament
  • Sacrotuberous ligament
• How does the anterior sacroiliac ligament differ from the posterior sacroiliac ligaments?

  The anterior sacroiliac ligament is broad and flat, while the posterior ligaments are thicker and stronger
• What is the deepest and strongest posterior ligament of the sacroiliac joint?

  Interosseous sacroiliac ligament
• What are the accessory ligaments associated with the sacroiliac joint?

  Sacrospinous and sacrotuberous ligaments
• What is the function of the sacrospinous and sacrotuberous ligaments?

  To provide added stability to the sacroiliac joint
• How do the accessory ligaments help the sacroiliac joint?

  They help stabilize the sacrum on the innominate
• What type of joint is the hip joint?

  Synovial ball and socket joint
• What bones articulate at the hip joint?

  The head of the femur and the acetabulum of the innominate bone
• What is one of the primary functions of the hip joint?

  It permits a wide range of movements
• What type of cartilage lines the head of the femur?

  Hyaline cartilage
• hip movements

  • 3 degrees from freedom 
  • Flexion 
  • Extension 30 degrees
  • Abduction 45 degrees
  • Adduction 45 degrees 
  • Lateral rotation
  • Medial rotation
• How does the hip joint contribute to the body’s structure?

  It connects the lower limb to the trunk and is involved in the transmission of weight
• What factors determine the stability of the hip joint?

  The shape of the articular surfaces, strength of the joint capsule, ligaments, and muscles crossing the joint
• Why is the femoral head not completely covered by the acetabulum when standing?

  Because the anterosuperior aspect is exposed
• In which directions does the acetabulum face?

  Laterally, anteriorly, and inferiorly
• What completes the inferior deficiency in the acetabulum rim?

  The transverse ligament
• What is the function of the acetabular labrum?

  It deepens the acetabulum and holds the femoral head firmly in the socket
• What shape is the acetabular labrum in cross-section?

  Triangular
• Where does the acetabular fat pad lie?

  Within the acetabular fossa
• What type of capsule surrounds the hip joint?

  Fibrous capsule
• How does the thickness of the fibrous capsule vary?

  It is slightly thicker anteriorly and superiorly
• Where does the joint capsule attach on the acetabulum?

  Directly to the bone outside the labrum above and behind, and to the bone and outer edge of the labrum in front and below
• Where does the joint capsule attach on the femur?

  Anteriorly to the intertrochanteric line and posteriorly to the neck of the femur
• What are the main ligaments associated with the hip joint?

  • Iliofemoral ligament
  • Pubofemoral ligament
  • Ischiofemoral ligament
• What is the state of the hip joint ligaments when standing?

  All three ligaments are under moderate tension
• What happens to the hip joint ligaments during hip flexion?

  All ligaments are relaxed
• What happens to the hip joint ligaments during hip extension?

  All ligaments are taut
• How do the hip joint ligaments behave during abduction/adduction and medial/lateral rotation?

  The behavior of the ligaments differs
• hip muscles

  • Flexion
  • Iliopsoas, Sartorius, Rectus Femoris, Tensor Fascia Lata
  • Extension
  • Glut max, Semimembranosus, Semitendinosus, Biceps Femoris
  • Abduction
  • Gluteus Medius and Minimus, Tensor Fascia Lata (in hip flex.)
  • Adduction
  • Pectineus, Adductor Magnus, Longus and Brevis, Gracilis
  • Medial Rotation
  • No prime movers but those ant. to hip axis can produce medial rotation i.e. anterior part of gluteus medius and minimus, Tensor Fascia Lata
  • Lateral Rotation
  • Obturators, Gemelli, Quadratus Femoris, Piriformis, Posterior Gluteus Medius, Superior Gluteus Maximus
• nerve supply

  • Posterior-extensors = sciatic nerve
  • Lateral - abductors = gluteal nerve
  • Anterior-flexors = femoral nerve
  • Medial-adductors = obturator nerve
• blood supply

  The hip joint receives its blood supply from the medial and lateral circumflex femoral arteries, the obturator artery and the superior and inferior gluteal arteries
• common pathologies

  • Hip fractures and trauma
  • Rheumatological conditions – OA and RA
  • Osteonecrosis
  • Infections in the bones and joints
  • Bursitis
  • Legg-Calve-Perthes disease
  • Developmental hip dysplasia
  • Femoroacetabular impingements (FAI)
  • Greater trochanteric pain syndrome (GTPS)
  • Adductor related groin pain (ARGP)
  • Proximal neuropathy