What is the net effect on femur height when PI raises femur 4 mm and EX raises femur 2 mm?

• A. Lower 2 mm
• B. Raise 6 mm
• C. Raise 2 mm
• D. No change

Answer: (B)

When multiple adjustments affect the same vertical measurement, their effects add if they act in the same direction. Here, both PI and EX raise the femur height—4 mm from PI and 2 mm from EX. Adding them gives 4 mm + 2 mm = 6 mm, so the net change is a rise of 6 mm. If the adjustments acted in opposite directions, you’d subtract the smaller from the larger to get the net effect.