What is the observed femur height change when 10 mm AS is corrected?

• A. -4 mm
• B. -2 mm
• C. +4 mm
• D. No change

Answer: (A)

When a 10 mm atlas subluxation is corrected, the body’s kinetic chain responds through the spine and pelvis, and that shows up as a measurable change in femur height. The atlas sits at the top of the spine, and bringing it toward neutral reduces vertical misalignment and the torque that travels down the spine. As the spine realigns, the pelvis often level and the sacroiliac joints adjust, which changes how one femur rests relative to the other. In this pattern, the observed femur height typically decreases by about 4 mm. So after the correction, you’d expect a −4 mm change in femur height.

This negative sign simply reflects the femur height becoming shorter on the measurement side as the pelvis rebalances. The other options don’t fit the common response pattern: a smaller change, a change in the opposite direction, or no change would not align with the usual kinetic-chain adjustment seen after a 10 mm atlas correction.