In a series of pictures uploaded to Instagram, Lukaku is seen receiving treatment at the Move to Cure clinic in Antwerp, Belgium.
The company specialises in the rehabilitation of professional athletes and non-athletes suffering from orthopaedic injuries – Lukaku injured his ankle in Uniteds win over Arsenal.
Manchester United still have three Premier League fixtures remaining but the clubs focus has turned to the FA Cup as Jose Mourinho looks to add another trophy to his impressive collection.
Lukaku, who joined the Red Devils from Everton last summer, was sent for scans on his ankle this week and United are confident he will be fit to face Chelsea at Wembley.
Lukakus presence would be a huge boost for United as they look to finish their season on a high – the 24-year-old has scored 27 goals for the club this season.
Manchester United booked their place in the FA Cup final with a 2-1 victory over Tottenham, while Chelsea beat Southampton the following day.
Asked about Lukakus injury at the weekend, manager Mourinho said: I dont know. To be out is not OK.
He wants to always play all the time, he is never tired, so when he has small things he doesnt care, he wants to go.
To say immediately “change” is because he couldnt play. But, three more weeks until the final. I just know [the injury] is on his foot.