It was a moment that would warm the heart of footy fans everywhere.

Alex Johnson, one of the most injury-cruelled players in the game, stepped foot on the SCG on Wednesday to run his first full lap in over three years.

The 24-year-old, who last played in the Sydney Swans' 2012 Premiership, has had a torrid time getting back to full fitness after first rupturing his ACL during a pre-season game the following year.

After an initial 12-month rehab, Johnson played in a reserves match in 2014 only to re-rupture the same knee.

He's had multiple setbacks and complications since due to infection, resulting in five knee reconstructions overall and countless more operations in an ongoing effort to get it back to square one.

His fifth - and hopefully last - reconstruction came in June earlier this season, a procedure labelled an overwhelming success.

He started running with the help of an AlterG (Anti-Gravity Treadmill) last week but Wednesday morning marked the first time in 906 days Johnson had run outside and at a sufficient pace.

Under the watchful eye of fitness staff, Johnson was first put through some strength and activation exercises before lacing up for a series of timed jogs.

He received a round of applause from teammates and staff before setting off on the first lap, and then every lap after that, each lap sweeter than the last for the comeback kid who's spent more of his football career in hospitals and rehab than actually running around playing the game.

The defender will look to increase his workload slowly and steady over the coming weeks.

Johnson is remaining hopeful of becoming the first player in the history of the game to make a comeback from five knee reconstructions.

He has managed 45 AFL games since arriving in Sydney via Pick 44 in the 2010 National Draft.

 

Alex Johnson glances over to teammates after his first lap in nearly three years.

Teammates and football staff were there to cheer AJ on.

All smiles as Johnson gets the a-okay from fitness staff.

 

Johnson shares a few laughs with teammates after the session.

 Positive steps!