A gran was left in agony after bungling surgeons put an implant in the wrong leg during her double knee replacement operation.
Barbara Barnes, 74, went under the knife two years ago to have an implant put in her right knee but surgeons accidentally put it in her left joint instead.
Since then, she has endured months of pain and has had to have further surgery to fix the implant in the right knee as well as more corrective operations in the future.
East Cheshire NHS Trust admitted the mistake which happened at Macclesfield Hospital but Mrs Barnes has now instructed solicitors Irwin Mitchell to investigate her treatment.
The gran, who has four grown-up children and seven grandchildren, said: "I had been struggling with my knees for years, so getting the green light on the replacements was exciting.
"However, after the first procedure, something just didn't seem right. I was extremely worried that something had gone wrong, but kept being told that everything was fine.
"Being told that a right-sided implant had been used on my left knee was a huge shock.
"It's the kind of basic error that you would not expect when undergoing major surgery. I still can't believe it happened.
"The issues raised by the investigation were very concerning, but it is at least welcome that measures can be taken to prevent this from happening to anyone else.
"You put a huge amount of trust in doctors and something like this impacts on that massively.
"I just hope that the NHS prevents this issue from happening again."
After suffering with knee problems for many years Mrs Barnes, who is married to John, 73, opted to have a double knee replacement.
She was due to have her left knee operated on first in October 2018, but after the surgery she was still in pain.
In January last year the National Joint Registry, the body which monitors the performance of replacement implants, contacted East Cheshire NHS Trust concerned about irregularities in four cases.
Following a review, Mrs Barnes' case was identified and a report found that the type of implant Barbara had were stored together, with left-sided items on the right side of the box, and right-sided items on the left.
The Trust also said how it was standard practice for three checks to be carried out on a knee implant- one by a member of the theatre team, then by scrub nurse and thirdly by the surgeon.
The Trust deemed that the checking process was not robust enough and have since made changes to procedures.
The checking procedure in theatre has also been amended to ensure the doctors and scrub nurses read the information on the item.
Rebecca Hall, specialist medical negligence lawyer at Irwin Mitchell, said: "This is a hugely concerning case in which clear issues, which you would struggle to make up, have been identified.
"Some of the simple and preventable mistakes have gone on to have a profound effect on Barbara.
"Patients who undergo joint replacement surgery place huge faith in medical staff and cases like this only serve to undermine that.
"While nothing can make up for what Barbara has been through we are pleased that the Trust has admitted it failings and identified new procedures.
"It is vital that these new procedures are communicated to all staff and that policies are upheld at all time to improve patient care."