In an effort to regain his Pro Bowl form, Vikings left tackle Matt Kalil underwent surgery on both of his knees in January, USA Today's Tom Pelissero reports.
Respected surgeon Dr. James Andrews performed arthroscopic surgery both of Kalil's knees, then in March he received a treatment called Regennex in which blood is removed from the knee, processed and re-injected.
The report says Regennex is similar to the procedures NBA star Kobe Bryant has been getting in Germany for years.
Kalil rounded out his medical tour with platelet-rich plasma therapy, which is said to speed up the recovery process.
According to Viking Update, Kalil had his knees operated on immediately after the season to avoid lingering issues like he had following knee surgery in 2014. Kalil admitted that his knees were never truly healthy last season.
Vikings coach Mike Zimmer said Kalil, despite starting all 16 games for a third consecutive season, played through a lot of pain in 2014.
"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," Zimmer said at the recent NFL owners meetings, according to ESPN.
The numbers from STATS LLC show that Kalil allowed a career-worst 13.75 sacks last season, more than the combined 11 sacks he was charged with over the first two years of his career.
Earlier this week the Vikings picked up the 2016 option on Kalil's contract. The option is not guaranteed, so if Kalil struggles again in 2015 the Vikings can cut him without further obligation to his contract. If they keep him, he'll be due to make more than $11 million 2016.