Chris Weidman is set to return to the Octagon July 6th at UFC 162, when he squares off against Anderson Silva for the middleweight title. Weidman last saw action in the Octagon one year ago at UFC on Fuel TV 4, when he knocked out Mark Munoz in the second round. Chris underwent surgery in November 2012 to repair an injury to his right shoulder,
In a December 2012 interview, Weidman indicates that he injured the shoulder "doing routine wrestling" with a team mate, went for a double leg takedown and landed "really weird" on the shoulder. He suffered a torn labrum, a torn rotator cuff, and an AC joint separation. He also notes there "was a ligament in there that was slightly torn."
This is a lot of damage from a single traumatic injury. A dislocation of the shoulder joint could explain the torn labrum and torn rotator cuff, and the AC joint separation probably occurred due to direct impact on the outside of the shoulder. (Weidman describes the injury as a "hard slam.") By the time his fight with Silva comes around, Weidman will have a full seven months of rehab under his belt, and his shoulder should be at full strength.
If you are interested in what surgery is like for a torn labrum, check out this video. It is a bit technical, but is a great demonstration of what can be done through an arthroscope.
Just for fun, you should watch this brief video of Weidman as he awakens following his shoulder surgery.