One of the unluckiest players to ever play in the AFL - Sydney Swans defender Alex Johnson - is back on the track after almost three years.

Johnson has had a series of failed knee reconstructions because of ongoing infections, since rupturing his ACL in a pre-season game against Gold Coast in 2013.

The 24-year-old, who has not played at AFL level since the 2012 grand final, had opted for his fifth surgery earlier this year.

If the defender manages to get back playing he will be the first player to come back from five knee reconstructions.