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The Hip

Functions of the Hip
Joint Structure of the Hip
Kinematics of the Hip Joint
Muscle actions at the Hip Joint
Hip Joint Stability
Mechanism of Injury at the Hip Joint

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ObjectivesĄG After studying this topic, the students will be able to

  1. to identify the structure of the hip joint, including joint type, articular shape, and the surrounding tissues
  2. to describe joint motions occurring at the hip joint, including osteokinematic and arthrokinematic movements, muscle actions, and factors checking hip motions
  3. to understand the stability mechanism of the hip joint and the possible mechanisms of injury
  4. to identify the malalignment of the weight bearing joints in different cardinal planes
  5. to explicate the trabecular system and its relationship to weight bearing

  1. Neumann DA (2002).  Hip.  In Neumann DA: Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia: Mosby.  Chapter 12, pp. 387-433.
  2. Smith LK, Weiss EL, Don Lehmkuhl L (1996). Brunnstrom's Clinical Kinesiology, 5th ed.  Philadelphia, F. A. Davis.  Chapter 8, pp. 266-300.
  3. Nordin M & Frankel VH (2001).  Biomechanics of the hip.  In Nordin M & Frankel VH: Basic Biomechanics of the Musculoskeletal System.  Philadelphia: Lippincott Williams & Wilkins. Chapter 8, pp.202-221.

Functions of the Hip

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  • To provide stability for weight bearing, such as standing, walking, or running
  • To allow mobility of the leg in space
  • To transmit the loads from the upper body to the thigh and then to the lower leg
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    Joint Structure of the Hip

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    Hip Joint

  • proximal componentĄG pelvis
  • concave acetabulum that faces anterior, inferior, and lateral
  • distal componentĄG femur
  • concave femoral head that faces anterior, superior, and medial (anteversion)
  • joint typeĄG ball-and-socket joint
  • motionsĄG convex on concave
  • hip flexion/ extension
  • hip abduction/ adduction
  • hip external/ internal rotation
  • DOF = 3
  • closed-packed positionĄG maximum extension, abduction, and internal rotation
  • not associated with the position of maximum congruency (90º of hip flexion with moderate abduction and external rotation)
  • against 13% of body weight (swing phase) to 300% of body weight (stance phase) during walking
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    Acetabulum
  • cup-shaped bony structure formed by part of the ilium, ischium, and pubis (20%)
  • acetabular notchĄG imcomplete bony rim in the inferior pole, covered with transverse acetabular ligament
  • lunate surfaceĄG only the periphery of superior, anterior, and posterior articular surfaces are in contact with the femoral head
  • cartilage thicker peripherally and acetabulum labrum deepen the shape
  • diameter changes with loading
  • unloaded conditionĄG Acetabulum articular surface has a smaller diameter than that the femoral head
  • loaded conditionĄG Acetabulum cartilage deforms to become congruent with the femoral head
  • Hip Joint

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    Angle of Inclination

  • synonymĄG head-neck angle
  • angle between the longitudinal axis of the femoral neck to that of the femoral shaft in the frontal plane
  • statistics
  • normal adultsĄG 125º
  • newbornĄG 140-150º
  • frontal plane deformities
  • coxa valgaĄG angle of inclination > 125º
  • coxa varaĄG angle of inclination < 125º
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    Angle of Anteversion

  • synonymĄG angle of anteversion
  • angle of the longitudinal axis of the femoral neck to the line connecting posterior aspect of both femoral condyles in the transverse plane
  • statistics
  • normal adults and child > 6 years oldĄG 12-15º
  • newbornĄG 30-40º
  • transverse plane deformities
  • anteversionĄG resulting in toeing-in gait (¤ş¤KŚr)
  • retroversionĄG resulting in toeing-out gait (Ľ~¤KŚr)
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    Malalignment of Weight-Bearing Joints

  • genu valgum vs. genu varum
  • genu recurvatum
  • pes valgus vs. pes planovarus
  • pes equinus vs. pes calcaneus
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    Trabecular System of the Femur

  • functionĄG to accommodate to the mechanical stresses and strains created by the transmission of forces between femur and pelvis
  • classification
  • medial trabecular system
  • from medial cortex of upper femoral shaft radiating outward to superior cortex of femoral head
  • parallel to joint reaction force on femoral head during single leg stance
  • lateral trabecular system
  • from lateral cortex of upper femoral shaft radiating outward to inferior cortex of the femoral head
  • in response to forces created during hip abductor contraction or to tensile stresses created by gravitational moments of force on femoral head
  • accessory trabecular system
  • medial accessory
  • lateral accessory
  • zone of weakness
  • the area where the trabeculae do not cross at right angles
  • less reinforcement by trabeculae
  • more potential for injury
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    Kinematics of the Hip

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    Hip Flexion/ Extension

  • joint involvedĄG hip joint
  • plane of motionĄG sagittal plane
  • axis of rotationĄG a frontal axis passing through the center of the head of the femur
  • osteokinematic movements
  • range of motion (ROM)
  • hip flexionĄG 0-140º
  • hip extensionĄG 0-45º
  • closed kinematic chain motions
  • deep squatting
  • stance phase of the gait cycle
  • cycling
  • arthrokinematic movements (convex on concave)
  • hip flexionĄG spin with slightly posterior glide of the femoral head on the acetebulum
  • hip extensionĄG spin with slightly anterior glide of the femoral head on the acetabulum
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    Hip Abduction

  • joint involvedĄG hip joint
  • plane of motionĄG frontal plane
  • axis of rotationĄG a sagittal axis passing through the center of the head of the femur
  • osteokinematic movements
  • range of motion (ROM)ĄG 0-40º
  • closed kinematic chain motionsĄG to maintain a level pelvis in unilateral stance
  • arthrokinematic movements (convex on concave)
  • hip abductionĄG inferior glide of the femoral head on the acetebulum
  • Trendelenburg signĄG
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    Hip Internal/ External Rotation

  • joint involvedĄG hip joint
  • plane of motionĄG transverse plane
  • axis of rotationĄG a vertical axis passing through the center of the head of the femur
  • osteokinematic movements
  • range of motion (ROM)
  • internal rotationĄG 0-40º
  • external rotationĄG 0-45º
  • closed kinematic chain motions
  • arthrokinematic movements (convex on concave)
  • hip internal rotationĄG posterior glide of the femoral head on the acetebulum
  • hip external rotationĄG anterior glide of the femoral head on the acetebulum
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    Muscles Across the Hip

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    Hip Flexors

  • iliopsoasĄG hip flexor
  • tensor fasciae lataeĄG hip flexor, abductor, and internal rotator
  • originĄG crest of the illium, lateral to sartorius
  • insertionĄG iliotibial band (please check the origin and insertion)
  • sartorius and gracilisĄG hip flexor and knee flexor, and internal rotator
  • rectus femorisĄG hip flexor and knee extensor
  • pectineus, adductor longus, brevis, and magnusĄG hip flexor and adductor
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    Hip Extensors

  • gluteus maximusĄG hip extensor
  • hamstringsĄG hip extensor + knee flexor
  • gluteus mediusĄG hip extensor + hip abductor
  • piriformisĄG hip extensor + hip external rotator
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    Hip Abductors

  • gluteus mediusĄG hip abductor
  • originĄG crest and outer surface of the illium
  • insertionĄG greater trochanter
  • gluteus minimusĄG hip internal rotator abd abductor
  • tensor fasciae lataeĄG hip flexor, abductor, and internal rotator
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    Hip External Rotators

  • piriformis
  • obturator internus and externus
  • gemellus superior and inferior
  • quadratus femoris
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    Hip Stability

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    Factors Affecting Stability of the Hip Joint

  • bony configurationĄG the most important
  • cartilage
  • cartilage at acetabulum thicker peripherally
  • acetabulum labrum deepens the shape of the acetabulum
  • ligaments
  • iliofemoral ligament (Y ligament of Bigelow or Y-ligament)
  • from anterior inferior iliac spine to intertrochanteric line with 2 slips (medial and lateral fasciculi)
  • taut in hip hyperextension (both slips) and full external rotation (lateral fasciculus)
  • sway back posture
  • standing posture of patients with paraplegia
  • pubofemoral ligaments
  • from superior pubisc ramus and anterior and inferior rim of the acetabulum to blending with medial fasciculus of the iliofemoral ligament
  • taut in hip abduction and hyperextension
  • ischiofemoral ligament
  • from posterior and inferior rim of the acetabulum (ischium)  to the greater trochanter of the femur
  • taut in hip full internal rotation and hyperextension
  • ligamentum teres
  • no help for the stability of the hip
  • from the fovea of the femoral head to the transverse acetabular ligament of the acetabulum
  • extensive set of capsular ligaments Ą@
  • capsular ligaments
  • longitudinal fibers
  • circular fibers
  • large-size muscles
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    Mechanism of Injury at the Hip

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    Direct stress

  • femoral neck fracture
  • intertrochanteric fracture
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    Repeated stresses

  • degenrative joint disease (DJD) of the hip
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    Deformities

  • congenital dislocation of the hip (CDH)
  • developmental dysplasia of the hip (DDH)
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    Established on 12/11/2002 and Last Updated 12/17/2004 © 2004 Huei-Ming Chai, PhD PT          All Right Reserved