Dr. Neal ElAttrache, who performed the surgery at the Kerlan-Jobe Clinic, estimated the recovery time at approximately six months, which would jeopardize Machado's availability for the March 31 season opener at Camden Yards.
The 75-minute procedure included an arthroscopy and open reconstruction of the medial patellar femoral ligament. A hamstring tendon was used to graft a replacement for the ruptured ligament.
Machado tore the ligament after stepping on first base during a Sept. 23 game against the Rays at Tropicana Field. An MRI didn't reveal any damage to the ACL or MCL.
Team orthopedist Dr. John Wilckens and Dr. James Andrews told Machado that he could attempt to rehab the injury, but he elected to undergo surgery and avoid the risk.
Machado will spend a few weeks in Los Angeles before continuing his rehab in Miami.
The Orioles estimated Machado's recovery at four-to-six months after announcing last week that he would undergo surgery.
"Dr. ElAtrache is conservative and he's expecting it to be six months to full baseball activity," said executive vice president Dan Duquette.
Is Machado unlikely to be ready on opening day?
"I wouldn't say that," Duquette replied. "The goal would be to have him ready for opening day, but the real goal is to stabilize Manny. What needs to be done needs to be done for Manny to return to full baseball activities. So, he's got some work to do with his rehab, which I'm sure Manny will tackle with great vigor.
"The 4 1/2 to six months... it may take six months. That's all I'm trying to communicate. It's going to depend how Manny comes along. That's all.
"I'm sure Manny wants to do what he can to be ready for opening day, but he also wants to do all the work recommended to rehabilitate the injury."
As I pointed out last week, Danny Valencia is a natural third baseman and could fill in if Machado begins the season on the disabled list. Ryan Flaherty also is an option if he isn't the starting second baseman.
In his first full major league season, Machado batted .283 with 51 doubles, 14 homers and 71 RBIs. Before the injury, he hadn't missed a game since being called up on Aug. 9, 2012.
Machado hyperextended the same knee at Single-A Delmarva in 2011, which is why he decided to have surgery today and avoid a potentially chronic injury.