ALLEN PARK — It’s still uncertain when Joique Bell will return to action following offseason surgery on his knee and Achilles.

The Detroit Lions running back will start training camp on the physically unable to perform list and coach Jim Caldwell said on Friday that there is no exact timetable for his return.

“I’m not sure how long it’s going to take. I do know one thing he’s coming along quickly. We’ll see what the doctor says. We can’t put an exact timetable on it right now,’’ Caldwell said.

Bell did not participate in organized team activities or minicamp in the spring, although he was on the field watching.

“From a schematic standpoint, he understands and knows how to run the ball, he knows the system and we’re just majorly concerned right now with getting him healthy and he’s well on his way to that,’’ Caldwell said on Friday.

He was healthy enough to make a trip to Britain a few weeks ago to represent the Lions and the NFL to promote the Lions-Chiefs game at Wembley Stadium on Nov. 1.

Right tackle LaAdrian Waddle and defensive end Jason Jones will also start the season on PUP.

“They’re all making excellent progress,’’ Caldwell said.

The Lions’ veterans report on Sunday and start training camp on Monday.

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