The document discusses the anatomy and biomechanics of the hip joint. It describes how the hip joint is stabilized by bony architecture and surrounding muscles. During single leg stance, the body weight acts at a greater lever arm than the abductor muscles, so the abductors must generate a force three times the body weight to counteract the torque from the weight. Clinical implications include techniques to reduce joint reaction forces, such as increasing the offset of a femoral component in a hip replacement.

1. HIP BIOMECHANICS
DR LUKMAN AL-NOMANI

2. OUTLINE
 Introduction
 Anatomy
 biomechanics

3.  BIOMECHANICS – Science that deals with the
study of forces (internal or external ) acting on
the living body
 The hip is a true ball-and-socket joint
surrounded by powerful and well-balanced
muscles
 Mobile as well as stable

4. ANATOMY

6. ANATOMY
 Stability
 conferred by bony architechture
 augmented by acetabular labrum and hip capsule
 Acetabulum
 anteverted 15 degrees
 abducted 45 degrees (caudal tilt
 femoral neck
 anteverted 15 degrees (in relation to femoral condyles)
 neck shaft angle of 125 degrees

7. HIP FUNCTIONS:
 Flexion :120 degrees
 Extension :5-30 degrees
 Abduction : 45 degrees
 Adduction :20-30 degrees
 Internal / external rotation : 45 degrees

8. HIP BIOMECHANICS
Biomechanics- HIP Fulcrum (hip joint) forces on either side
of fulcrum i.E, body weight & abductor tension

9.  To maintain stable hip, torques produced by the
body weight is countered by abductor muscles
pull. Abductor force X lever arm1 = weight X
leverarm2

10. FORCES ACTING ACROSS HIP JOINT
 Body weight
 Abductor muscles force
 Joint reaction force

11. JOINT REACTION FORCE
 force generated within a joint in response to
forces acting on the joint
 in the hip, it is the result of the need to balance
the moment arms of the body weight and
abductor tension
 maintains a level pelvis

12. BILATERAL LIMB STANCE
 the centre of gravity is located between the two
hips, with an equal force exerted on both hips.

13. SINGLE LEG STANCE
 Centre of gravity moves distally and away from
the supporting leg
 The non-supporting leg becomes a part of the
body mass .
 The abductors resisting the rotation of the
femoral head
 The lever of the abductors is shorter than the
lever arm of body weight. Therefore, the
combined force of the abductors must be
multiples of body weight (typically three times
body weight),

14. CLINICAL IMPLICATIONS
 Actions that decrease joint reaction force include
 acetabular side
 moving acetabular component medial, inferior, and
anterior
 femoral side
 increasing offset of femoral component
 long stem prosthesis
 patient's gait
 shifting body weight over affected hip this results in
Trendelenburg gait
 cane in contralateral hand
 reduces abductor muscle pull and decreases the moment
arm between the center of gravity and the femoral head

15. THANK YOU
 References:
 https://www.physio-
pedia.com/Biomechanics_of_the_Hip
 https://www.orthobullets.com/recon/9064/hip-
biomechanics