"Jordan's surgery went really well and we anticipate that he should be able to make a full recovery for the start of next season," Cooper said in a team release.
This is the second season-ending knee surgery for one of RSL's eight academy products on the roster. Allen's rookie season was cut short in 2014 when he underwent microfracture knee surgery that kept him out for nearly a year. In his fourth year at RSL, Allen has had 50 league appearances with four goals and four assists. He signed a new multi-year contract extension in February.
After a promising preseason, he entered the year as a starter in RSL's 4-3-3 formation. But a quadriceps injury at Chicago on March 11 forced him to miss the next three months as his recovery process was slowed by a hamstring injury during a match with Real Monarchs.
Allen returned to the RSL starting lineup in the 4-1 loss to Sacramento Republic FC in the U.S. Open Cup on June 14, but came off after 45 minutes.
Earlier this week, RSL coach Mike Petke was asked about Allen's availability going forward.
"He took another 10 steps back," Petke said, referencing this injury. "It's been frustrating for him, it's been frustrating for us, and hopefully he gets healed this time and we can get some consistency."
A day after returning from the Open Cup loss, Allen said he was happy to be back on the field after missing another significant chunk of the season.
"It's been frustrating, obviously," he said. "I wanted to have a really good start to this year and it hasn't worked out like that, but now it's just about making up for lost time."
Another lengthy rehabilitation process awaits, which unfortunately for the talented Allen has become all-too-familiar.