Western Bulldogs premiership forward Clay Smith has announced he will retirement from AFL football, effective immediately.

The 25-year-old has been struggling with an on-going knee injury, and hasn't played an AFL game in 2018, with his last appearance for the club coming in round 20, 2017.

“It was a very difficult decision for me to retire at my age, but the right one to make given my knee hasn’t been able to fully recover,” Smith told westernbulldogs.com.au.

“I’ve given everything to try to make it back this season, but unfortunately it hasn’t worked out the way I would’ve liked.

“I want to thank everyone at the Western Bulldogs for their support over my career, and especially the medical staff, physios and strength and rehab staff for their care and professionalism.

“It’s been a difficult road for me, but I was able to experience being in the premiership team and I wouldn’t swap that for anything.

“I’ve also met some great people, made some incredible friendships, and I’m grateful to have had the opportunity to play AFL football.

“While life without footy will leave a big hole in my life, it has shaped me as a person and helped me grow and I’m thankful for that.”

Smith played 55 games for the Bulldogs including 13 in their premiership year, and kicked 43 goals during his time at Whitten Oval.

In arguably one of his most important and impressive performances, Smith booted a career-high four goals in their preliminary final triumph over the Giants in 2016.

Smith suffered ACL injuries in 2013, 2014 and 2015, before returning to play in the Dogs' drought-breaking flag.