Altuve's knee injury which caused him trouble throughout the season was an avulsion fracture, Brian McTaggart of MLB.com reports.
An avulsion fracture occurs when a small piece of bone attached to a ligament or tendon gets pulled away from the rest of the bone. He had surgery to fix the problem Friday and is expected to be fully recovered by the start of spring training. The second baseman's numbers took a step back across the board following his MVP campaign in 2017, with his slash line falling from .346/.410/.547 to a still excellent .315/.385/.449. His homers dropped from 24 to 13, while he stole 17 bases after swiping 32 bags the season before. Given the severity of his knee injury, however, the dip appears to be very understandable, and there's reason to believe he'll bounce back next season.