Of course, I think. Mom misses her three-legged walker that allows her the freedom to keep up with much younger people. Me, for instance. Even new knees probably won't get her back to playing tennis, riding horses or driving a car, as she did well into her 70s. But they'd make it possible for her to walk to the bathroom, to the dining room and mailbox, and through the malls and thrift stores with me.
Quality of life is a relative term.
She's different from my Dad, who gave up and crawled into bed when he couldn't have the life he'd always had. Mom is feistier and more determined. So when her surgeon asked me if I thought the surgery would improve my mother's quality of life, I didn't hesitate. Mom has a whole lot of living left to do. The old gray mare might not be what she used to be, but she's a long way from dead.