Picken collided into Lai in the third quarter of the Dogs' 28-point loss to Fremantle when he attempted to smother a point-blank shot at goal by Michael Walters.
Lai was standing with his legs straddled when contact was made, which saw his left leg buckle inwards.
The incident was purely accidental.
Lai, a doctor, suspected a torn anterior cruciate ligament when he was taken to the rooms, and it was later suggested he had also injured his medial ligament.
"It was a bit of a blur, really," Picken told AFL.com.au after the game.
"I just tried to smother the ball and I fell into [Lai]. I was just trying to stop [Walters] kick that goal and it was right on the goal line so it was just unlucky.
"I can't really remember what happened. I just remember seeing trainers around him.
"He's just been really unlucky and it's one of those things that happens.
"I hope he's doing alright and makes a speedy recovery."
Play was halted for around five minutes while Lai was stretched from the field, with members from both clubs' medical staff carrying him from the 'Footscray End' to the race.
The AFL's protocol when it comes to the medical treatment of umpires sees the responsibility held by the clubs.
Umpires have a trainer and physiotherapist at their disposal throughout games but rely on the medical support of clubs – which they are paid for – when the occasional injury strikes.
The delay in deploying a stretcher to Lai came as the clubs didn't realise how badly hurt the goal umpire's knee was.
Fremantle coach Ross Lyon said while the injury to Lai was concerning, the stop in play affected his players' momentum after they opened the third quarter with goals to Kepler Bradley, Hayden Crozier and Walters.
"I though the start of the third we jumped right out and used the ball beautifully and scored quite well and then unfortunately, the goal umpire got hurt and it put a stop to that run," Lyon said.
"I think we'd kicked three in nine minutes.
"It's the least of our worries – to see someone get hurt, and it seemed quite seriously, it is a concern, obviously.
"In the context of the game, it probably wasn't ideal."
Fremantle captain Matthew Pavlich kicked the game's next goal but the only other two majors for the third quarter went the way of the Bulldogs.
Liam Picken is a defender in NAB AFL Fantasy. He averaged 75.91 points in 2012. Register your team at our AFL Fantasy Hub.
Jennifer Phelan is a reporter for AFL Media. Follow her on Twitter @AFL_JenPhelan.
