3 fused bones of the ilium, ischium, and pubis, whenpaired up these form what is called the pelvic girdle.

Sacroiliac joint is where the ilium interfaces with the sacrum.

Acetabulum is where the femur from the upper leg articulateswith the pelvis.

Greater trochanter

front

Femur

Tibia

fibula

Example 5.5

FM is the magnitudeof the resultant forceexerted by the hipabductor muscles

FJ is the magnitude ofthe JRF applied bythe pelvis on the femur.

W1 is the weight of theLeg

W is the BW as a ground reaction forceon the one leg

O is the axis ofrotation of the hipjoint.

A is where the hipabductor musclesattach.

B is the COG of theleg

C is where groundreaction force isapplied to the foot

a,b,c are distancesas shown, note thata is distance betweenA and O and gets resolved into ax andAy

Find the force exertedby the hip abductormuscles (gluteusmedius and minimus)and the JRF tosupport the hip andthe leg as shown

Alternative hip solution

Concurrent forces withline of actions intersectingat Q

Total BW – weight of theright leg

Note that left leg is raisedfrom the floor

Note that you get the same answers for FM and FJ

x

y

ax = a cos , ay = a sin

bx = b cos , by = b sin

cx = c cos , cy = c sin

Once again a concurrentsystem of forces

Carefully read and review all of Chapter 5