HIP JOINT
Definition
The hip joint is a ball-and-socket synovial joint formed by the articulation of the head of the femur and the acetabulum of the pelvis.
Location
Located where the upper end of the femur meets the pelvic bone.
Type of Joint
A strong ball-and-socket type synovial joint that permits a wide range of movements.
Articulating Surfaces
- Head of femur
- Acetabulum of hip bone
- Both surfaces covered by hyaline cartilage
Structure
- The head of the femur fits into the cup-shaped acetabulum.
- The joint capsule surrounds the joint and attaches to the acetabular rim and intertrochanteric line.
- The acetabular labrum deepens the socket.
- Synovial membrane lines the capsule and secretes synovial fluid.
- Ligamentum teres connects the head of femur to the acetabulum.
Ligaments of Hip Joint
- Iliofemoral ligament
- Pubofemoral ligament
- Ischiofemoral ligament
- Ligamentum teres
- Transverse acetabular ligament
Development
- Develops from fusion of primary ossification centers: • Head and shaft of femur • Ilium and ischium
- Acetabulum forms from fusion of three secondary ossification centers: • Acetabular fossa • Acetabular margin • Transverse acetabular ligament
Nerve Supply
- Femoral nerve → anterior aspect
- Obturator nerve → medial aspect
- Sciatic nerve → posterior aspect
- Superior gluteal nerve and nerve to quadratus femoris also contribute
Blood Supply
- Medial circumflex femoral artery
- Lateral circumflex femoral artery
- Obturator artery
- Superior and inferior gluteal arteries
Lymph Drainage
- Lymph drains mainly to superficial inguinal lymph nodes via femoral canal.
Movements of Hip Joint
- Flexion
- Extension
- Abduction
- Adduction
- Medial rotation
- Lateral rotation
- Circumduction
Muscle Action Sequence
- Extension → Gluteus maximus, hamstrings
- Flexion → Iliopsoas, tensor fasciae latae
- Abduction → Gluteus medius, gluteus minimus
- Adduction → Adductor group
Stepwise Anatomical Mechanism
-
Extension: 1 → Gluteus maximus contracts → 2 → Femur rotates laterally → 3 → Hip joint extends
-
Flexion: 1 → Iliopsoas contracts → 2 → Femur rotates medially → 3 → Hip joint flexes
Clinical Anatomy
- Posterior hip dislocation is most common → limb becomes flexed, adducted, internally rotated
- Fracture neck of femur → may cause avascular necrosis of femoral head
- Trendelenburg gait → due to gluteus medius weakness or superior gluteal nerve injury
- Osteoarthritis → degenerative changes causing pain and stiffness
- Slipped capital femoral epiphysis → femoral head slips from neck (adolescents)
- Leg-length discrepancy → affects posture and gait
- Femoroacetabular impingement → abnormal contact between femur and acetabulum