Kalil also had injections to help manage joint pain. Both knees were scoped in January before having a Regenexx procedure performed on them in March. Kalil also had platelet-rich plasma therapy performed, too.
Throughout the procedures, Kalil has been working out and rehabbing at the Vikings' team facility.
Picking up Smith's option was a simple one for the Vikings, as he picked up 92 tackles and grabbed five interceptions for Minnesota last season. He's scheduled to make $5.278 million next year.
Kalil was a more difficult decision, as the former No. 4 pick has struggled after a strong start. His salary would be over $11 million in 2016.
"His knees were hurting a lot, bothering him, but he'll be important to our success, as well -- making sure that he plays good, which will allow us to play better."
Kalil, who had left knee surgery before last season, has started all 48 games since being drafted in 2012. Minnesota must decide in May whether to pick up Kalil's fifth-year option.
"He might play great 70 plays, and eight plays he's not very good at all," Zimmer said. "We have to make him more consistent. We have to get him to finish better. I'm encouraged with some of the things he talked to me about the other day."
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