Ben, a golden retriever puppy with chestnut eyelashes, seemed to be an uncommonly good dog.

He was playful but polite. He did not jump on visitors, the way young retrievers often did.

“I remember, when we first got him, thinking, ‘This is so amazing, this dog doesn’t jump,’” said his owner, Beth Yaroscak.

Soon she learned why: Ben could not jump. He had hip dysplasia, a common, painful and often crippling joint defect in which the ball of the femur rubs against the hip socket rather than rotating smoothly. Ben needed help getting up onto a couch or bed, and at the end of a normal day he was worn out like an old hound.

This is how, in late January, at the age of 9 months, Ben found himself etherized on a table at the Animal Medical Center on the Upper East Side, about to undergo an operation usually thought of as the province of older humans: a hip replacement.