RETIRED Carlton forward Andrew Walker has revealed the debilitating pain he endured throughout his career — and the wonder drug that helped heal his arthritic knee.

Walker battled a range of knee issues throughout his career, undergoing four surgeries and extensive rehabilitation, before his pain crescendoed in 2014.

The 31-year-old lost 10 kilograms that season, as the mental anguish that walked hand-in-hand with his physical torment took over his life.

Walker’s pain was so severe he contemplated undergoing an osteotomy — surgery that breaks the leg to change the force that drives through the knee joint.

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But Walker and Carlton discovered a WADA-approved wonder drug called pentosan. There would be no more surgery, just injections of the drug.

“What it has done for me in such a short term has been amazing,” Walker said on Fox Footy’s On The Mark.

“I think my bone bruising decreased significantly within about six months.

“The positive out of it is that it does actually work, even for elite athletes that are constantly putting their bodies under such duress.”

Andrew Walker retired at the end of 2016. Photo: Scott Barbour/Getty Images Source: Getty Images

A number of AFL players are currently injecting the same drug Walker used and is still using.

And while Walker conceded the lingering damage of the Essendon drugs scandal would affect the way people perceive the drug, he was confident no one would perceive him to be a drug cheat.

“I know the process we went through and it was a strenuous one,” Walker said.

“I was always conscious of what I was doing and what I was putting in my body.

“When you have the support of your club, the AFL and obviously WADA, I was really confident that what I was doing was right.”

Walker said towards the end of his career he was playing through unbearable pain, which affected him not only on the field, but at home.

“Trying to get up and play AFL footy, with something so significant, was really hard,” he said.

“I was probably playing each week with what I would call 9-10/10 pain.

“Footy’s hard enough, but when you chuck something like that on top of it it’s even more difficult.

“Throughout 2015 simple things like walking the dog, going to the kitchen to have coffee in the morning ... I just found myself leaning on walls to get down the hallway.”

Andrew Walker’s famous 2011 screamer. Source: News Limited

But despite Walker’s knee joint being arthritic — “basically bone on bone” — the Echuca product never dreamt of giving the game away prematurely.

“I never questioned whether it was worth it,” Walker said.

“We all love playing AFL footy and I was lucky enough to play for Carlton and got to play in front of really big crowds against Collingwood and Richmond so never did that thought go through my mind.

“It’s probably why I ended up in so much pain.

“As an elite athlete you want to go out there and perform and show the supporters what you can do. Unfortunately, being so proud probably caused those sorts of issues with my knee.”