Uelese was ruled out of the Wallabies' June Series on Sunday, with suspicions he had suffered the serious injury, and scans on Monday confirmed the worst-case scenario.
The 21-year-old was on the field for just 10 minutes in the Rebels' win over the Blues in Auckland before falling awkwardly in a tackle on Blues no. 8 Akira Ioane.
Uelese will go under the knife on Thursday, and begin the long rehabilitation process.
Rebels general manager - professional rugby - Nick Ryan, said the news was a blow to the team.