Ace the PTEACS Physical Therapy Exam 2026 – Get Moving and Master Your Future!

Seat depth determines how much of the thigh and buttock are supported by the chair. If the depth is too shallow, the posterior thighs don’t have adequate contact with the seat, the pelvis tends to tilt forward, and the base of support becomes unstable. That lack of stable support makes someone feel unsteady and like they might slip out of the chair. Proper depth keeps the thigh surfaces supported and the pelvis in a more neutral position, which helps maintain balance and a secure seated posture. A practical check is to ensure a small clearance behind the knee and enough depth so the back of the thighs are well-supported, with about 2–3 fingers of space behind the popliteal crease.