Eight out of 10 knee replacements and six out of 10 hip replacements last as long as 25 years, says a large study from the University of Bristol.
This is much longer than believed, the researchers said, and the findings will help patients and surgeons decide when to carry out surgery.
To date, there has been little data on the success of new hips and knees.
But this Lancet research looked at 25 years’ worth of operations, involving more than 500,000 people.
Hip and knee replacements are two of the most common forms of surgery in the NHS, but doctors often struggle to answer questions from patients on how long the implants will last.
Nearly 200,000 of the operations were performed in 2017 in England and Wales, with most carried out on people between 60 and 80 years old.
Dr Jonathan Evans, orthopaedic registrar, lead study author and research fellow at Bristol Medical School, said: “At best, the NHS has only been able to say how long replacements are designed to last, rather than referring to actual evidence from multiple patients’ experiences of joint replacement surgery.
“Given the improvement in technology and techniques in the last 25 years, we expect that hip or knee replacements put in today may last even longer.”
As the ageing population grows, and life expectancy rises, this becomes even more important, Dr Evans added. -BBC