Which statement is true regarding articular congruency of the hip joint?

a. The hip joint is not considered to be a naturally congruent joint.
b. The acetabulum is larger than the femoral head and entirely covers the head.
c. A combination of hip flexion, abduction, and lateral rotation gives the hip joint its most congruent position.
d. A combination of extension and adduction gives the hip its most congruent position.

ANS: C
The hip joint is considered to be a congruent joint. Although this is relatively true, there is substantially more surface area on the head of the femur than on the acetabulum. Articular contact between the acetabulum and the femoral head can be increased in a position of hip flexion, abduction, and slight lateral rotation. This position is often used for immobilization when the goal is to improve articular contact and joint congruency.