How is seat depth determined for a wheelchair user?

• A. Fixed at 18 inches for all adults
• B. Determined from the patient's posterior buttock along the lateral thigh to the popliteal fold
• C. Based on the user's height only
• D. Measured as the width of two fingers from the front edge of the seat

Answer: (B)

Seat depth is set by the length of the thigh to keep the front edge from pressing into the back of the knee and to ensure the footrest and leg support are properly positioned. To determine it, measure from the posterior aspect of the buttock along the lateral thigh to the popliteal fold (the back of the knee). This distance defines the seat depth, with a small allowance subtracted (about one inch to two inches) to prevent pressure behind the knee. Fixed depths for all adults, sizing by height alone, or using a width-based measure from the front edge do not account for individual leg lengths and can lead to poor fit or discomfort.