Five years ago, on a muggy August morning in Hicksville, N.Y., Ann Kornhauser was out walking her golden retriever when bones in her left foot suddenly cracked. Ms. Kornhauser, then in her late 50s, soon learned why: doctors discovered a rare tumor in her foot. They amputated half of it.

The prosthetic foot she received afterward left her in constant pain; she often cried in her car after trips to the grocery store because she dreaded carrying the bags into the house. Her prosthetist offered a solution. Artificial limbs had greatly improved, he said, and she could benefit from one of the new high-tech models — but it would fit only if her left leg was amputated below the knee.

The idea of losing the rest of her leg, which was healthy enough, seemed preposterous and frightening. But after two years of discomfort, Ms. Kornhauser decided to do it.

“All my family said was, ‘You’re going to be sitting there without a leg.’ But they didn’t know what I knew,” she said. “I knew it was going to look like a leg and that people ran marathons on them. I knew that I would have a life.”