What forces maintain A-P equilibrium of the hip joints in bilateral stance?

What will be an ideal response?

ANS:
A-P equilibrium of the pelvis requires no muscle activity in symmetrical bilateral stance. The gravitation line falls behind the hip joint, creating a hip extension or posterior pelvic tilt "moment" (torque). The extensor torque is offset by tension in the hip joint capsule and ligaments, with some possible contribution by the passive tone in the hip joint flexors.