ONE SERIOUS knee injury is tough for a player and his footy club to swallow, but two is shattering and throws up serious career ramifications for even the most talented players.
The past month has seen three players - Bulldog Clay Smith, Adelaide's Andy Otten and now young Giant Jonathon Patton - suffer the second anterior cruciate ligament injuries of their careers, requiring full reconstructions.
The spotlight this week is on Patton, who was a prized No.1 selection at the 2011 NAB AFL draft but has suffered serious knee injuries in each of his three seasons.
His case is among the unluckiest in memory. He played seven games in 2012 because of pre-season knee surgery and just three games in 2013 after he ruptured his right ACL.
The 21-year-old will now miss the next 12 months after another ACL injury, leaving doubts on whether he will be able to reach his undoubted potential.
Other current players to have undergone multiple knee reconstructions are Fremantle's Anthony Morabito, Geelong's Daniel Menzel, Swans Nick Malceski and Alex Johnson, and Hawthorn's Brendan Whitecross.
There are stories of triumph through adversity, but others struggle to reach the heights they could have if given a clean bill of health. looks at past players whose promising careers were shot down because of injury.
Matthew Egan (Geelong)
Geelong's best first-year player in 2005, Egan looked like a key defender you could build a backline around for a decade. Early in his career he shut down key forwards like Matthew Pavlich, Nick Riewoldt and Jonathan Brown, earning All Australian selection in 2007. In round 22 of that season, however, he fractured the navicular bone in his right foot, requiring emergency surgery. He missed the Cats' 2007 premiership and never played at AFL level again.
Max Bailey (Hawthorn)
Selection No.18 in the 2005 National Draft, Bailey suffered three ACL injuries in his 43-game career. He was, however, one of the great stories of Hawthorn's 2013 Grand Final triumph, earning a premiership medal in his final AFL game.
Jesse Smith (North Melbourne and St Kilda)
The son of former North Melbourne player Ross Smith, the midfielder won the 2004 Larke Medal as the best player in the Under-18 National Championships. He was drafted by the Kangaroos as a father-son prospect but missed the entire 2006 season with an ankle injury. In 2008 he managed just two games because of hamstring problems, which flared again in 2009. Drafted by the Saints at the end of 2009, he broke down with an ankle injury in 2010 and retired.   
Justin Longmuir (Fremantle)
Recruited with pick No.2 in 1998 National Draft, the tall forward arrived at Fremantle with high expectations and was an exciting player at his peak. He was restricted to 139 games, however, and forced into retirement at the end of 2007 because of a degenerative knee injury. In 2005 he played all but one game, memorably kicking an after-the-siren goal to seal victory against St Kilda in round 21. He would play just 19 more games, however, because of the knee issue.
Clem Michael (Fremantle)
The son of WAFL legend Stephen Michael, the ruckman played just 43 games between 1998 and 2000, claiming his career was ended because of inappropriate medical treatment. Michael tore the posterior cruciate ligament of his left knee in round four, 2000, but was only sidelined for two weeks, playing the remaining 16 games of that season with the assistance of painkilling injections. The Freo big man had experimental surgery on the knee at the end of the year but he never played again, retiring at the end of the 2002 season.
Luke Molan (Melbourne)
Part of the 2001 'Superdraft', Molan was recruited by Melbourne with pick No.9 but would not manage a single AFL game because of a shocking run with injury. The 192cm forward suffered a horrific broken leg playing for Sandringham in his first year at the Demons and was hit with another setback in early 2003, missing five game with a cartilage tear. Then, mid-season in the VFL in one ultimately career-ending contest, he suffered a broken collarbone, ruptured ACL and concussion. He was rookie listed in 2004 but that would be his last season in the AFL.
David Schwarz (Melbourne)
A star for Melbourne through the 1990s, 'the Ox' played 173 games between 1991 and 2002, winning the Dees best and fairest in 1999 and playing in the 2000 Grand Final. He was robbed of some of his best years, however, by three serious knee injuries that wiped out his 1995 and 1996 seasons. Schwarz said he avoided weights after his knee reconstructions to keep his weight down and he was able to push on for another six seasons.
Ryan Fitzgerald (Sydney Swans and Adelaide)
Now a recognisable personality on TV and radio, 16 years ago Fitzgerald was an exciting young forward recruited by the Swans with pick No.4 in the 1998 National Draft. A shoulder injury kept him out of action until the 2000 season but he made an impact on debut, booting five goals. In 2001 he suffered a knee injury that required a reconstruction, missing the entire season. Traded to hometown club Adelaide, he suffered another ACL injury and retired after a total of just 18 games.
Luke Penny (Western Bulldogs and St Kilda)
Recruited by the Bulldogs with pick No.14 in the 1998 National Draft, Penny played 35 games for the club before he was traded to the Saints in 2002. The key defender sustained a posterior cruciate ligament injury in his right knee midway through 2003 and could never fully recover. He shocked the Saints with his decision to retire at the age of just 24 and with three years remaining on his contract. He played 45 games for the Saints.