Biomechanics Hip

Question 1

hip

-primary functions

Answer 1

supports the head, arms, and trunk
static erect postures
dynamic postures
-ambulation, running, stair climbing

Question 2

hip degrees of freedom

Answer 2

3

• abduction/adduction
• flexion/extension
• IR/ER

Question 3

hip arthrokimenatics

• type of joint
• movement rule

Answer 3

ball and socket

convex on concave (glide and roll opposite directions)

Question 4

hip loose pack position

Answer 4

35 degrees flexion/abduction

slight external rotation

Question 5

hip closed pack position

Answer 5

maximum extension
maximum IR
maximum abduction

Question 6

hip articular components

Answer 6

articular surfaces
-acetabulum
-head of femur
joint capsule
-thick and tough

Question 7

hip capsular ligaments

-anterior or posterior

Answer 7

iliofemoral or "Y" ligament
-anterior
pubofemoral
-anterior
ischiofemoral
-posterior

Question 8

acetabular labrum

• what is it
• where does it accach?
• which portions most innervated
• blood supply mostly _____

Answer 8

ring of fibrocartilage that encircles the acetabulum
attachments
-rim of acetabulum
-transverse acetabular ligament
anterior and superior portions most innervated
blood supply mostly peripheral (outer 1/3)

Question 9

labrum functions

Answer 9

shock absorption and pressure distribution
-increases surface area of acetabulum by 20%
-distributes load and decreases contact stress
joint lubrication
-maintains synovial fluid within articular cartilage
–allows for some load to be borne by fluid pressurization
enhances joint stability

Question 10

acetabulum is positioned in what position (relative to cardinal planes)

Answer 10

lateral
inferior
anterior

Question 11

why does the upper portion of the acetabulum form an overhang - purpose

Answer 11

sustains highest forces through femoral head

Question 12

where is the articular cartilage thickest for the femoral head and acetabulum

Answer 12

superiorly

Question 13

where is the one point the femoral head is not covered in articular cartilage

Answer 13

fovea

-ligamentum teres attachment

Question 14

in which plane do the following occur

• angle of inclination
• angle of torsion

Answer 14

inclination
-frontal
torsion
-transverse

Question 15

angle of inclination in

• infants
• adults
• elderly

Answer 15

infants
-150
adults
-125
elderly
-120

Question 16

do females have a greater or smaller angle of inclination than men?
-why

Answer 16

smaller

-greater pelvic width

Question 17

coxa valga and coxa vara angles

Answer 17

valga
-angle > 125
vara
-<125

Question 18

what knee posture is associated with

• coxa vara
• coxa valga

Answer 18

coxa vara and genu valga

coxa valga and genu vara

Question 19

angle of torsion

-what two structures is the measurement between?

Answer 19

long axis of femoral head

transverse axis of femoral condyles

Question 20

angle of torsion

-typical measurement

Answer 20

adults - around 12

can range from 8 to 25

Question 21

anteversion and retroversion

• measurement
• consequence

Answer 21

anteversion
-angle > 12
-IR of femur
retroversion
-angle < 12
-ER of femur

Question 22

cantilever system of the hip

• what is it?
• purpose

Answer 22

forces transmitted to the femoral shaft through the femoral neck
gives us a larger moment arm

Question 23

significance of long femoral neck

• benefit
• negative

Answer 23

improves mechanical advantage of hip abductor muscles

causes femoral neck to be susceptible to fractures with bone weakening

Question 24

hip joint capsule

• what is it’s shape?
• attaches to…

Answer 24

shaped like a cylindrical sleeve
attaches to
-entire periphery of the acetabulum via labrum
-neck of femur

Question 25

“accordion-like” folds found on inferior and superior aspects of capsule

• what are they called?
• what’s their purpose

Answer 25

frenula (synovial folds)

required to permit full abduction and adduction ROM

Question 26

hip capsule ligaments

• do they wrap in CW or CCW direction
• why this direction?
• consequence

Answer 26

CW direction
direct result of development of upright posture
primary reason why humans have extremely limited hip hyperextensiion

Question 27

ligamentum teres

-function

Answer 27

does not function to support joint

serves as a guide for obturator artery branch traveling to fovea on head of femur

Question 28

closed chain motion of the hip and the corresponding open chain motion

Answer 28

anterior/posterior pelvic tilt
-flexion/extension of hip
lateral pelvic tild
-abduction/adduction of hip
anterior and posterior pelvic rotation
-IR/ER

Question 29

double-leg stance

• where is COM
• muscle action required
• static structures required

Answer 29

whole body COM acts at S2 and is midline
no muscle activity required to maintain upright, neutral posture at the hip
ligaments and joint capsule provide stability

Question 30

trendelenburg sign

-what occurs at the pelvis, femur, and lumbar spine (standing on R leg)

Answer 30

pelvis
-contralateral (left) lateral tilt
femur
-ipsilateral (R) adduction
lumbar spine
-ipsilateral (R) lateral flexion

Question 31

primary muscles used during unilateral stance that act in the frontal plane

Answer 31

ipsilateral hip abductors (glut med)

contralateral erector spinae