Rooney is expected to be out until April but could have potentially ruled himself out until the end of the year had the injury damaged his anterior cruciate ligament.
The Englishman will definitely miss his international friendlies under Roy Hodgson against Germany and the Netherlands on March 26 and 29 but is expected to be it in time for euro 2016.
Van Gaal admitted earlier this month that Rooney may have made the problem worse by not telling him he was in pain, which sounds like something he’d definitely do, but by all accounts it may well have been worse.
Any serious injury like that would have seen Rooney sidelined for at least six months and he’s no spring chicken, so I doubt United would sit and wait around for him to return without considering bringing in a replacement straight away.
As for his future at the club, I’ve made my opinion clear that I thought he’d leave in the summer but at that time I didn’t think Jose Mourinho was going to replace van Gaal. Were that to happen, he wouldn’t be going anywhere because Mourinho has always wanted him as a player.
For the time being, United have to cope without having Rooney until April and that means he’ll miss both Europa League ties against Liverpool plus the crucial derby which could make or break or top four hopes this season.