LAKE FOREST – Bears receiver Johnny Knox has not watched the replay of the hit that broke a vertebra in his lower back and put his NFL career on hold.

Knox doesn’t plan to watch the replay from Dec. 18 anytime soon, either.

“I probably don’t want to see it until I retire,” Knox said Wednesday at Halas Hall.

Knox watched the Bears’ organized team activities from the sidelines, and it’s uncertain when he will be able to join the action on the field. He acknowledged a possibility that he might miss the upcoming season but hoped otherwise.

“It could happen,” Knox said, “but I’m staying optimistic. My main focus is on the weight room. That’s all I’m focused on. I’m not in a rush.

“This is my spine, the core of my body I’m dealing with. It’s not my knee or my ankle or my shoulder. I’m taking my time.”

Knox, who was listed at 6 feet and 180 pounds at the start of last season, said he lost about 30 pounds after his back surgery. He has regained about 10 pounds and hopes to add more through weight training, although he can only train with machine weights now because trainers fear that using free weights could lead to a setback.

Knox said he spent three days in the hospital and wore a back brace for 2½ months after his surgery. That was not easy for a player whose elite speed helped him tally 2,214 receiving yards and 1,506 return yards in three NFL seasons.

“It was tough at first, but I got used to it,” Knox said. “But it was all for a good reason. My doctors and the training staff stayed hard on me, wanting me to keep me in it, because it helped me get right.”

Knox said he never allowed a “Why me?” attitude to slow his progress.

“Since Day One, my mindset has been real positive,” Knox said. “No letdowns. No setbacks. I’m surrounded by a great group of people, a great organization, friends, family and they’re keeping me positive, and I’m just staying positive and moving forward.”

Bears bits: The Bears signed defensive tackle Nate Collins to a 1-year contract to increase their roster to 90 players. Collins, 24, appeared in 13 games in the past two seasons with the Jacksonville Jaguars as an undrafted free agent out of Virginia. … Chris Williams, who played left guard last season, shared snaps at left tackle with incumbent starter J’Marcus Webb.