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BIOMECHANICS AND
ERGONOMICS 1
DPT
BIOMECHANICS OF
Hip joint
• LECTURE # 01
Objective
•
•
•
To identify the structure of the HIP JOINT ,
including joint type, articular shape, and the
surrounding tissues
To describe joint motions occurring at the hip
joint , including osteokinematic and
arthrokinematic movements, muscle actions,
and factors checking hip motions
To understand the hip joint stability and the
possible mechanisms of injury
Basic function of lower extremity
• Upper limb is specific for more specialized
activities in large ROM
• Lower Limb main function is weight
bearing.
• Maintenance of balance
• Also involved in activities such as kicking,
performing lower and high jump.
Functions of the Hip
• To allow mobility of the leg
• To transmit the loads from the upper body to the thigh
and then to the lower leg
• Participate in elevating and lowering the body as in
• Climbing
• Raising from chair
• Bringing the foot towards the body or hand
• For total mobility hip motion is accompanied by the
movement of the lumber spine
Structure of the Hip joint
•ball-and-socket joint
• head of femur
• acetabulum
• heavy joint capsule
• many reinforcing ligaments
• less freedom of movement than shoulder
joint
Hip Joint vs. Shoulder Joint
Hip Joint is a weight bearing joint, shoulder is not
Acetabular fossa deeper than glenoid fossa so hip has
more bony support than shoulder
Hip has much stronger ligamentous support
In the hip joint mobility is sacrificed for the sake of
stability
Both are ball and socket joints
Each has a laburm to increase socket depth
The Hip Joint
Articular Surfaces
Femoral Head
•Approx. 70% of
the femoral head
articulates with the
acetabulum
Acetabular Labrum
& Acetabulum
.
Type: Synovial Ball-and-Socket
Joint
The Hip Joint- ligaments
Ligament of the
Head of the Femur
(Lig. Teres)
Transverse
Acetabular Lig.
Ligaments
iliofemoral ligament (Y ligament)
• Cover the hip joint anteriorly and
superiorly
• taut in hip hyperextension (both slips) and
full external rotation (lateral fasciculus)
Ligaments
•
•
•
•
pubofemoral ligaments
Anterior and inferior to the hip joint
taut in hip abduction and hyperextension
Limit the motion of external rotation
Ligament
• ischiofemoral ligament
– taut in hip full internal rotation and
hyperextension
– Limit the internal rotation
• 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
• Abduction of the hip is limited by tension
on the pubofemoral and ischiofemoral
ligament
• Adduction in limited by tension of the
superior portion of y ligament
Factors Affecting Stability of the
Hip Joint
bony configuration： 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)
Motion of the Hip Joint
Flexion
Hyperextension
Abduction
Extension
Adduction
Motion of the Hip Joint cont.
Medial Rotation
Lateral Rotation
Types of Movement
•
•
different bones will move depending upon
whether the limb is in weight bearing or non
weight bearing
Weight bearing (fixed) -foot in contact with
ground and the limb is supporting weight of
body
–
–
•
Pelvis moves on a fixed femur
Bending down to touch toes
Non Weight bearing (free) - foot free of
ground and the limb is unable to support
weight of body
–
–
Femur free to move on a fixed pelvis
Kicking a ball
joint Structure of the Hip
• proximal component： pelvis
– concave acetabulum that faces anterior,
inferior, and lateral
• distal component： femur
– Convex femoral head that faces anterior,
superior, and medial
• joint type： ball-and-socket joint
• motions： convex on concave
– hip flexion/ extension
– hip abduction/ adduction
– hip external/ internal rotation
Hip Joint – Capsule
Most Capsular Fibers Run Longitudinally and
Obliquely
5-6 mm. proximal to
•
the acetabular margins
Intertrochanteric line
Ant. view
Midway along femoral neck
Post. view
Anatomic and mechanical axes of
femur
Anatomical axis
• Represent by a line through the femoral
shaft
• The neck of the femur form an angle of
about 125 degree with the anatomic axis
of the femur
Angle of Inclination
(Between the femoral neck and
shaft)
Approx. 125o
•The angle of
inclination is
measured in the
frontal plane and
typically ranges from
115 to 140 degrees.
Angle of Inclination
• synonym： head-neck angle
• angle between the longitudinal axis of the
femoral neck to that of the femoral shaft in the
frontal plane
• statistics
– normal adults： 125º
– newborn： 140-150º
• frontal plane deformities
– coxa valga： angle of inclination > 125º
– coxa vara： angle of inclination < 125º
Angle of Inclination
Coxa Vara
• An angle between
femoral neck and shaft
less than 115°; increases
stress on femoral neck.
• This:
1. shortens the limb;
2. decreases the
effectiveness of the
abductors;
3. increases the load on the
femoral neck;
4. reduces the load on the
femoral head.
Coxa Valga
• An angle between femoral
neck and shaft greater than
140°; increases pressure
into the joint
• This:
1. lengthens the limb;
2. mimics contracture of the
hip abductors;
3. reduces the load on the
femoral neck;
4. increases the load on the
femoral head.
Angle of Torsion
The angle between the axis of the neck and
the transverse axis that passes through the
femoral condyles
a
Normal
b
12o -14o
Retroversion <12o
c
Anteversion >15o
Angle of Ante version
• 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 old： 12-15º
– newborn： 30-40º
Excessive Anteversion
•An increase in the
angle of torsion
(anteversion)
influences the rotation
of the limb and
produces a toe in gait
(pigeon toes).
Retroversion
•A decrease in the
angle of torsion
(retroversion)
influences the
rotation of the limb
and produces a toe
out gait (duck feet).
transverse plane deformities
• anteversion： resulting in toeing-in gait
• retroversion： resulting in toeing-out
gait
Toeing in gait