From Canadiens Communications -
Alexei Emelin underwent a reconstructive surgery to his left knee (ACL & MCL). His recovery is estimated to be 6 months.
The 27-year-old defenseman suffered a torn ligament in his left knee after colliding with Boston Bruins forward Milan Lucic during a tilt on April 6 at the Bell Centre. In 38 games during the 2013-13 campaign, Emelin collected three goals and nine assists, while also registering a plus-2 differential. In addition to seeing his ice time increase from an average of 17:17 per game in his rookie year to 19:40 this past season, Emelin led the Canadiens in hits for a second consecutive season with 110, while also picking up 47 blocked shots.
Here is the video of the April 6th incident