Seat depth measurement is taken from where, and what adjustment is recommended?

• A. From posterior buttock to popliteal fold; depth increased by 2 inches
• B. From posterior buttock to popliteal fold; depth increased by 0 inches
• C. From anterior superior iliac spine to popliteal fold; depth decreased by 2 inches
• D. From posterior buttock to popliteal fold; depth decreased by 2 inches

Answer: (D)

Seat depth is the distance from the back edge of the buttock (posterior buttock) to the popliteal fold. The correct adjustment is to decrease this depth by about 2 inches to provide clearance behind the knee and prevent the seat edge from pressing into the popliteal area. Measuring from the posterior buttock ensures you account for how the pelvis and thigh sit on the seat, giving accurate fit. Using a measurement from a different landmark (like the ASIS) would read the depth incorrectly, and increasing the depth or leaving it unchanged would risk knee pressure and poor circulation.