Biomechanics of Hip and Pelvis Flashcards
Describe the sagittal plane of motion for the hip.
anterior/posterior tilt
describe the frontal plane of motion for the hip.
left lateral pelvic tilt (left side moves upward)
right lateral pelvic tilt (right side moves upward)
describe the transverse plane of motion for the hip.
left transverse pelvic tilt (left side moves posterior)
right transverse pelvic tilt (right side moves posterior)
what is the angle of inclination formed by?
angle in teh FRONTAL plane formed by the axis of the head and neck of the femur and shaft of the femur
what is the angle of inclination in infants?adults?
infants- 150 degree
adults- 125 degrees
(the angle of inclination decreases by 25 degrees from infancy to adulthood)
what is a decrease in the angle of inclination called?
coxa vara (genu valgum)- distal femur is directed towards the midline and the knees are closer together
what is an increase in teh angle of inclination called?
coxa valga (genu varum) - distal femur is directed away from the midline and the knees are farther apart
what is the purpose of normal inclination angle?
allows abductors to function with a mechanical advantage as they counterbalance body weight in one-legged stance
where should hip abductors be to achieve muscle stability which is maximum when the child begins to stand? (one-legged)
hip abductors should be as far laterally from the hip (fulcrum) to increase the lever arm
what is alsberg’s angle?
(similar to angle of inclination) - angle formed by the line thru the epiphyseal plate of the neck of the femur and the long axis of the femur
what is normal alsberg’s angle?
41 degrees
an increase in alsberg’s angle would be called what? a decrease?
increase- coxa valga (genu varum)
decrease- coxa vara (genu valgum)
what is the angle of declination?
angle in the TRANSVERSE plane formed by the axis of the neck of the femur and the transcondylar axis of the knee with the apex of teh angle lateral
what is the angle of declination in infants? adults?
infant: 30-60 degrees of internal rotation
adults: 8-12 degrees of internal rotation
what is femoral anteversion?
normal internal femoral shaft rotation for angle of declination
Name the hip external rotators.
*mnemonic- go out and get some quality players gluteus maximus obturators adductors gemelli sartorius quadratus femoris piriformis
Name the internal hip rotators.
gluteus medius and minimus
what is the normal fetal position?
(like buddha)
hips and knees flexed
hips externally rotated
legs and feet internally rotated
what allows maximal rotation of hip in flexed position?
femoral anteversion
what is teh angle of inclination?
angle created from the adducted position of the femur
how do you calculate neutral femoral position (NFP)?
NFP = max. external rotation - (external rot+ internal rot/2)
what does a negative value for NFP indicate?
there is more internal rotation than external rotation
if NFP is the same with the hip flexed and extended, what does this indicate?
rotation is due to bony changes (in femur)
if NFP is different btwn hip flexed and extended, what does this indicate?
rotatio is due to a soft tissue contracture
what is the NFP for infants?
(3:1 ratio)
external- 60- 90 degrees
internal- 0-30 degrees
what is the NFP for up to 1 y/o?
(2:1 ratio)
external- 50-60 degrees
internal- 30 degrees
what is the NFP for up to 4y/o?
(1:1 ratio)
external- 45 degrees
internal- 45 degrees
which ligament is tightened with the hip flexed?
ischiofemoral ligament
what could be a cause of decreased internal hip ROM (same as increased external hip ROM)?
shortened or taut ischiofemoral ligament
which ligament is tightened with hip extended?
iliofemoral, puboscapular, ligamentum teres
what could be the cause of decreased external hip ROM (same as increased internal hip ROM)?
shortened or taut iliofemoral, puboscapular, ligamentum teres
what is the needed amt of hip flexion/extension?
flexion- at least 120-130
extension- 0-20
what is the needed amt of hip abduction/adduction?
hip abudction- 40-45
hip adduction- 20-25
what are you testing when you have patient supine, flex the hip and knee to 90 and slowly rotate the leg outwards (externally) as you gradually extend the knee?
testing medial hamstring tightness
-examiner will be unable to achieve 160 degrees of knee extension
what are you testing when you have patient supine, flexed hip and knee, and slowly rotate the knee internally as you gradually extend the knee?
testing lateral hamstring tightness
