After redshirting in 1999, McKinnie started his junior and senior years at left tackle for the Hurricanes. During his college career, he was an extraordinary blocking tackle, not allowing a sack on a quarterback against opposition such as future NFL star Dwight Freeney from Syracuse. McKinnie was, however, penalized for holding Freeney on one play, a rare blemish on his memorable season. McKinnie received first-team All-American honors in 2000, and was recognized as a unanimous first-team All-American in 2001. Also in 2001, McKinnie was the winner of the Outland Trophy, finished 8th overall in voting for the Heisman Trophy, was the CNN Sports Illustrated “Player of the Year” and a key part of the Hurricanes’ 2001 National Championship. At Miami, he was roommates with future NFL tight end Jeremy Shockey.

McKinnie was selected seventh overall by the Minnesota Vikings in the 2002 NFL Draft. McKinnie started every game for Minnesota from 2003 to 2007, and had a streak of 80 consecutive games started.

In October 2005, McKinnie was charged with a misdemeanor for his involvement in the Minnesota Vikings boat party scandal.

On May 26, 2006, McKinnie pleaded guilty to disorderly conduct and being a public nuisance on a watercraft in connection with the Love Boat scandal. He agreed to pay a $1,000 fine and perform 48 hours of community service. Vikings owner Zygi Wilf said, in addition to community service, he would participate in numerous service events this season. On September 9, 2006, the NFL announced that it would fine McKinnie and fellow Viking Fred Smoot one game check for the incident. For McKinnie, it amounted to approximately $41,000. A day after the fine was levied, he was given a raise and a seven-year extension of his contract worth $48 million.

In February 2008 McKinnie was arrested and charged with aggravated battery, disorderly conduct and resisting arrest without violence after a street brawl outside a Miami nightclub. Miami police said McKinnie spit in the face of a bouncer when he was removed from the club, then, after heading across the street to another establishment, returned to Club Space and argued with the bouncer, Eric Otero. McKinnie then allegedly shoved his phone in Otero’s face before picking up a heavy pole and hitting him. A judge ordered McKinnie to complete 25 hours of community service and anger management classes. He also served a four-game suspension during the 2008 NFL season following the incident.

After a 2009 loss against the Arizona Cardinals, it was reported by Tony Boselli on the Dan Patrick show that McKinnie accidentally tipped off the Vikings offensive game plan to the Cardinals. He said that the Cardinals knew when the Vikings were going to pass because of his leg. “He would have one of his legs back a little bit further” when getting in stance before the play. In 2010, McKinnie allowed a sack that injured Brett Favre and stopped his consecutive regular season start streak at 297 games.

In the summer of 2011, McKinnie was placed on the Vikings’ non-football injury list for reportedly showing up to camp out of shape, according to The Star Tribune. He had finished the prior season at 360 pounds and claimed he was going to hire a trainer in the offseason to help him lose some weight. He had also been taking tennis lessons from Venus Williams during that time and claimed that the lessons were long and tired him out. He was eventually released on August 2, 2011.

After former University of Miami teammate Ed Reed vouched for him as a strong player, McKinnie signed with the Baltimore Ravens on August 24, 2011.

McKinnie tested free agency for a little over a month following the 2012 season, but the Ravens ultimately signed him on May 2, 2013 to a two-year deal valued at up to $7 million.

On October 21, 2013, The Ravens traded McKinnie to the Miami Dolphins for a conditional late-round draft pick for the 2015 NFL draft.