The number of patients in Wales waiting more than a year for surgery has gone up by 400% in just four years.
The Royal College of Surgeons asked every health board in Wales how many people had been on the waiting list for longer than 52 weeks.
Its Freedom of Information requests revealed that in March 2017 there were 3,605 patients waiting over a year, compared to 699 in March 2013.
David Roberts, a 70-year-old widower from Amlwch on Anglesey, has been on a waiting list for a knee replacement since November 2016.
He's been warned the wait could be as long as 98 weeks, forcing him to rely on painkillers to control his arthritis.
The former PE teacher told ITV News: "The pain is getting worse. I know it comes down to funding but I've always been active and now I'm finding it harder and harder to get around."
Earlier this month, the Welsh Labour Government promised to spend an extra £50 million from its reserves to bring down waiting times.
But the problem - driven largely by a rapidly ageing population - isn't confined to Wales.
The latest statistics from NHS England show the number of people waiting more than six months for an operation has almost tripled in the same period to 126,188 in March 2017, compared to 45,054 in March 2013.
But there are far fewer waits of over a year in England - with 1,302 patients compared to 3,605 in Wales, despite a population 17 times the size.
Responding to Wednesday's figures, the Welsh government acknowledged some patients were waiting too long.
"Despite increased demand on the NHS in Wales, the health service is treating more patients, with the vast majority being seen within target times," a spokesperson said.
"Over the last five years, referrals to hospital-based services have increased by around 20% - from 1.07 million in 2012/13 to 1.27 million in 2015/16.
"Despite this, latest figures show over half of patients are waiting less than 10 weeks for treatment."
But Mr Tim Havard, Regional Director for Wales at the Royal College of Surgeons and a consultant general surgeon, believes there are still too many patients filling hospital wards who should be getting social care at home.
He said: "NHS Wales and the Government must give renewed focus to policies that will help decrease waiting times.
"In particular, we’d like to see better provision of out-of-hospital services and more protection of beds used for planned surgery.
"Long waits for surgery can be traumatising for patients and their families.
"A patient's condition can also deteriorate the longer they are made to wait for treatment, meaning the eventual outcomes are not as good as they could have been."