My mom has knee pain and this is the one mattress feature she can't sleep without — 5 beds you can find it in during Memorial Day sales

A woman sits on the edge of Plank Firm Mattress on a bed frame in a bedroom, demonstrating the excellent edge support of this mattress. A Tom's Guide price drop deals graphic in the bottom right corner.

My mom can drift off pretty much anywhere, from a packed bus to a hotel by London's busiest tube station. But there's one place she refuses to sleep: on a mattress with poor edge support.

This isn't my mom being a prima donna. She has bad knees and needs a stable base to press against when getting on and off a mattress. That's what edge support provides.