After making a return from injury in November's Premier League draw at Ipswich Town, Luke played in subsequent victories against Bodo/Glimt and Everton, both at Old Trafford.
On Tuesday evening, he posted the following statement on social media:
"Hi guys, it's hurting a lot having to write this as I really thought I had got through my recent struggles and was on a positive path going forward, but unfortunately I've had a small setback. I've been through a lot and had a lot of ups and downs but this has definitely been my toughest period. I'm absolutely devastated and it's extremely tough to come to terms with reality at this moment in time.