The surgery was performed by Dr. Rick Wright, Dr. Matt Matava and Dr. Matt Smith at Washington University Orthopedic Center in Chesterfield.
Gunnarsson suffered the injury during the first period of the Blues' 4-1 win over the Vancouver Canucks on March 23.
He will be re-evaluated in six months.
Gunnarsson, 31, dressed in 63 games for the Blues this season, posting nine points (five goals, four assists) and 22 penalty minutes. The 6-foot-2, 198-pound defenseman is currently in his fourth season with the Blues after the club acquired him via trade from the Toronto Maple Leafs on June 28, 2014.
Overall, the Orebro, Sweden, native has appeared in 556 career NHL regular season games, amassing 122 points (25 goals, 97 assists) and 151 penalty minutes.
