The 20-year-old midfielder returned to United’s Carrington training base for medical assessment after sustaining the knee injury, with scans confirming the seriousness of the problem. He is expected to miss the remainder of the season.
Moorhouse joined Dundee on loan on transfer deadline day after spending the previous campaign with Leyton Orient. The move was intended to give him further senior experience in Scotland, and he had made two appearances in the Scottish Premiership before the injury.
He made his debut with a 45-minute appearance against Hearts, who beat Dundee 2-1. Moorhouse was then included in the starting line-up for the following fixture, helping the Dark Blues secure a 2-1 victory over Motherwell.
The injury occurred during a match against Partick Thistle, when Dundee initially hoped the knee problem would prove minor. Further assessment revealed the damage was much more serious, ending his loan spell prematurely.
Moorhouse had attracted interest from other clubs during the summer, but Dundee secured his services to strengthen their midfield options. His progress at Leyton Orient had also helped raise his profile, making the Scottish move an opportunity to build on his first experience of senior football.
The setback is particularly difficult for Dundee, who have been hit by a series of serious knee injuries. Moorhouse is the third player at the club to suffer an ACL injury this season, following Simon Murray and Fin Robertson.
The sequence has prompted concern at Dens Park, with the club examining whether there could be any common factors behind the injuries. Dundee manager Steven Pressley has also explored the possibility of bringing in free agents to help cover the resulting shortage of players.
For Manchester United, the priority will be supporting Moorhouse through rehabilitation. An ACL injury typically requires a lengthy recovery period, with the player needing to rebuild strength and regain confidence before returning to competitive football.
The midfielder remains under contract at Old Trafford, where he has been regarded as a promising academy product. His loan was designed to accelerate his development by exposing him to the demands of regular senior competition.
Instead, the injury has brought that progress to a halt. Moorhouse now faces a long rehabilitation programme before he can resume his career, with his immediate focus on recovery rather than a return date.