A knee-replacement implant, used in thousands of UK operations, was known to have a concerning failure rate eight years before it was finally withdrawn, the BBC has discovered.
Patients have told File on 4 Investigates how they were left immobile or addicted to painkillers after receiving the NexGen knee implant, because it ended up slipping out of place. Hundreds of people have now had to undergo a second corrective operation.
Knee surgeons say the implant's US manufacturer, Zimmer Biomet, took too long to acknowledge there was a problem with one particular component.
Zimmer Biomet says patient safety is its "top priority" and that its products are approved in accordance with the relevant regulations.
Debbie Booker from Southampton had an operation to replace her left knee in 2016.
Although initially it appeared to have been successful, she started to experience severe pain a year later while on holiday in Majorca.
"I laid a bag of ice on my knee and for four days I had to do that every few hours because I was in agony," she says.
A knee replacement involves removing damaged surfaces of the femur (thigh bone) and the tibia (shin bone) and replacing them with artificial components.
Debbie says the pain resulted from the knee implant slipping from the tibia and wearing away the bone.
Over the next few months she says she became reliant on prescription painkillers: "I was on fentanyl and morphine. It took me a long time to come off of the morphine because I was addicted."
She has since had a second knee replacement, but the problems caused by the initial failed implant have caused long-lasting health problems, she says.
"It's put my whole body out of alignment, I walk with a limp," says Debbie. As a result, she is now awaiting a hip replacement.
Another patient, "Diana" (not her real name), had a knee implant fitted in 2021 which also slipped and started to wear away her shin bone, leaving her virtually immobile.
"The consultant told me every time I stood up, I was standing on a broken leg. It was absolute agony," she says.
Diana asked to be anonymous as she used to work in the NHS.
As part of their knee replacements, both Debbie and Diana had received a specific implant section, known as a "stemmed option tibial component", also known as a "tibial tray".
In broad terms, this section lacked a layer of plastic contained in earlier, well-regarded versions of the NexGen replacement knee.
Date: 12 August