A fit, hardworking young tradie with his whole future ahead of him, Cooper Sterling never imagined that a dull ache in his knee would turn into the fight of his life.
The 22-year-old construction worker from Beaumont Hills in Sydney was, by his own admission, just like any other young bloke - working hard, having beers with mates, and spending weekends with his girlfriend, Tori.
But late last year, his world was turned upside down after what he thought was nothing more than growing pains spiralled into a devastating cancer diagnosis.
'It was a pain that I've never really felt before,' Cooper told Daily Mail.
'I wasn't able to fully bend my knee; it hurt to walk, it hurt when I was doing nothing lying in bed. It would just throb.'
After what started as a dull ache, soothed only by Voltaren and Nurofen just to get through the day, Cooper's knee only got worse.
By December, the pain had become so bad he struggled to bend his leg. Still, he soldiered on - even going on a cruise with Tori despite being in constant agony.
'I actually told her before we left, "I don't know if I'll be able to go because my knee is killing me,"' he recalled.
Not wanting to ruin their trip, he pushed through but was in excruciating pain the whole time.
Back home in January, Cooper finally reached breaking point. After yet another night of sleepless agony, he told his father he couldn't take it anymore and booked in for tests.
What happened next was a blur. In one day, he had an ultrasound, an X-ray, and was called back for further scans, including an MRI and CT.
Within hours, his GP phoned him, urging him to come back in immediately and to bring a support person.
'The first thing I asked was, "Am I going to die?"' Cooper said.
'And my doctor just said, "I can't give you that answer." That was the scariest moment of my life.'
A biopsy days later confirmed his worst fears. Cooper had osteosarcoma - a rare and aggressive bone cancer most common in teenagers and young adults.
'I'd never even heard of it before,' he said. 'I was in complete shock.'
Through that appointment, Cooper tried to stay positive. His grandmother had beaten lung cancer, and so had his aunt with breast cancer, so why couldn't he too?
Two weeks later, he began chemotherapy. The treatment was, in his words, 'awful.'
'I was violently sick every day, and I couldn't keep any food down.
'I lost dangerous amounts of weight that got so bad they were contemplating me not having the surgery at all.'
Even worse, after four rounds of chemo, the tumour wasn't shrinking. It was still growing and was becoming dangerously close to wrapping around his main artery.
His surgeons laid out the stark options: they could attempt to cut the tumour out, but there was no guarantee they'd get it all.
Even a single cell left behind could mean the cancer returned. The safer choice, they said, was amputation.
'I wanted to get back to my life as soon as possible, so for me, the amputation was a no-brainer,' Cooper said.
'I told them right there on the spot: "take the leg."'
In March 2025, Cooper underwent major surgery to remove his leg 12cm above the knee - it was a major success.
'They cut out 100 percent of my cancer. I didn't get an infection; I didn't even get a runny nose. I felt very, very blessed.'
Within 48 hours he was up on a walker, and he left the hospital just nine days later. By his side through every step was Tori.
'I haven't slept a night in hospital alone. She's always slept in recliner chairs next to me through my chemo.
'And when I asked her parents for their blessing to marry her, I told them the truth - I wasn't scared of dying; I was scared of leaving her behind.'
In July, just months after his surgery, Cooper proposed.
'The moment I got diagnosed was the moment I knew I didn't want to grow old without Tori,' he said.
'I wanted her to know that any sacrifice she made for me during this cancer journey would be worth something and we could look back on this time in a positive way.'
Far from letting cancer define him, Cooper has become determined to use his story to help others.
He started documenting his journey online, drawing thousands of supporters.
'So much of what you find when you Google a cancer diagnosis is doom and gloom,' he explained.
'I wanted to show people that it isn't necessarily a death sentence.'
He has also thrown himself into fundraising, and after only three months post-surgery, he and a mate will tackle 100km as part of the Go the Distance campaign for Sydney's Chris O'Brien Lifehouse cancer centre.
Together, they've already raised $18,000.
'I'm doing laps at my local sports centre, pushing myself more each day. It's a way to give back but also to prove to myself what I'm capable of,' he said.
With treatment nearly behind him, Cooper is looking forward to getting back to work, moving in with Tori, and starting the next chapter of his life.
'The world feels like it's opened back up again,' he said. 'Tori and I are slowly working through everything. We've both had to step away from our careers to tackle this head-on but now we're ready to rebuild. Moving in together would be nice too.'
Looking back, he said the amputation that once seemed like a nightmare has become his greatest blessing.
'I feel very lucky that I got the chance to lose my leg because the alternative could have been not being here at all,' Cooper said.
'Life's too short to take for granted. I know that now more than ever.'