In that excruciating moment as the Swans' Alex Johnson fell over the boundary line clutching his knee, the thought of everyone watching in a deafeningly quiet MCG was a unanimous "Please no!".

Key points: The LARS procedure is said to cut recovery time by eight months

The LARS procedure is said to cut recovery time by eight months Current and former Sydney Swans Alex Johnson, Rhys Shaw and Mick Malceski have all undergone the surgery

Current and former Sydney Swans Alex Johnson, Rhys Shaw and Mick Malceski have all undergone the surgery Gemma Etheridge had the LARS operation in order to compete in the 2016 Olympics, where she won a gold medal

Johnson's tear-streaked face spoke of his mental anguish at the thought of having to go through yet another knee reconstruction for a shredded anterior cruciate ligament (ACL) and yet another year of rehab after six years out of the game he loves so much.

The Australian rugby sevens Olympic gold medallist Gemma Etheridge gets it.

Crying, she said: "I don't even know the guy, but it's tough. I don't know how he does it."

Etheridge has had three knee reconstructions of her own.

The last was a LARS operation: The Ligament Augmentation and Reconstruction System uses a synthetic rope-like structure to replace the damaged ACL.

For a time around seven to eight years ago, LARS was touted as a miracle cure.

Sportsmen and women lined up for the operation with the promise of returning to the field after just four months, as opposed to the normal 12 months for a conventional ACL reconstruction.

The poster boy for LARS was the former Swans AFL player Nick Malceski, who was the first to have the operation in 2008.

Swans defender Nick Malceski is among a list of athletes who have undergone the procedure. ( Dave Hunt: AAP Image )

When that failed in 2011, he had another and was back on the field within 11 weeks.

Others followed, including the Swans' Rhys Shaw, rugby league player Luke Covell and golfer Nick O'Hern.

What is an ACL? The anterior cruciate ligament is an important ligament that helps stabilise your knee

The anterior cruciate ligament is an important ligament that helps stabilise your knee Torn ACLs can cause the knee to collapse when trying to twist or turn

Torn ACLs can cause the knee to collapse when trying to twist or turn Repairing torn ACLs typically requires replacement tissue from somewhere else in the body

Repairing torn ACLs typically requires replacement tissue from somewhere else in the body Australian rules football, rugby, soccer and netball are all high-risk sports Source: Better Health Channel

Dr David Broe, an orthopaedic surgeon who practices at Sydney's Prince of Wales Hospital, explained the difference in recovery time.

"When you put in a normal ACL graft, that graft goes through four stages of healing and in one of those stages, the graft gets a little bit weaker, classically from the six to 12 week mark. And then after that the graft lays down new collagen and develops a blood supply and gets stronger from there," Dr Broe said.

"What they thought the beauty of the synthetic graft was, that it would not go through that weakened stage and the patients could get going with their more strenuous rehab earlier and quicker and could be back to running and more aggressive pivoting activity at an earlier date."

But for the successes there were also failures, including Alex Johnson who had two unsuccessful LARS operations in his run of wretched luck.

And it's those failures which is why LARS has now been widely condemned by knee surgeons like Dr Broe.

"It was too good to be true. The problem being that they just didn't biologically incorporate properly, and they had a much higher than anticipated failure rate and there were lots of recorded revision surgeries. People became very wary because it was felt that it was essentially unsafe to use, Dr Broe said.

"The problem was when they failed you were left with this synthetic debris floating around in the joint which caused synovitis, which is an inflammatory reaction in the joint and caused a lot of recurrent knee swelling and instability."

It may also lead to premature arthritis, warns the Australian Orthopaedic Association's Australian Knee Society.

Dr Broe has done just one LARS operation.

His patient was Gemma Etheridge.

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At the time she was 31 and just four and a half months shy of representing Australia in the first ever rugby sevens Olympic competition.

"It was a very innocuous training incident, I just stepped off my leg and it sort of collapsed under me. I'd had two before and I knew the feeling and I instantly knew what I'd done," Etheridge said.

Suddenly three years of work was looking like it was wasted.

And so she took a leap of faith and after much consultation decided to have the LARS operation.

"I thought if I can just get through this one block before I retired, I'd be happy."

It paid off.

Just four months later, Etheridge won an Olympic gold medal.

Dr Broe said it was only exceptional circumstances and Etheridge's health that prompted him to take on her operation.

"We've seen too many bad cases. I got a winner with that case, yes, however there have been too many bad cases," Dr Broe said.

The days of the quick fix via LARS are over, but the good news is that a conventional reconstruction need not mean 12 months on the sideline.

As Alex Johnson weighs up his future, he of all people knows there is no miracle cure.

But it may be some solace to know that the thoughts of thousands of athletes, like Etheridge, who have gone through their own knee reconstructions, are with him.