Cristiano Ronaldo will require further specialist advice to discover the exact extent of his ankle problem.
Ronaldo reported the injury in the aftermath of Portugal's Euro 2008 exit and suggested he would fly back to Manchester for an operation.
But the 23-year-old did not return as United medical staff felt a period of rest, which Ronaldo was due anyway, was a better course of action.
However, Ronaldo has now met with medical staff from both Portugal and the Red Devils, with further information now being sought.
'Manchester United medical staff met with the medical team from the Portuguese FA and Cristiano Ronaldo in Lisbon today regarding the ongoing treatment of his injured right ankle,' said a statement released by United on Wednesday evening.
'As a result, further specialist advice is being sought and an announcement will be made on any action in due course.'
The information is awaited with intrigue given Ronaldo's present position.
Should it be decided an operation is required, it could have a major impact over the Madeira-born winger's fitness for the start of the new season, which in turn may determine how far Real Madrid are willing to push their attempts to lure him away from Old Trafford.
Although Sir Alex Ferguson's squad began training today, Ronaldo is not due back in England for another fortnight.
Ferguson is yet to speak to Ronaldo about the large number of statements from Madrid - which went unchecked by the player - during Euro 2008.
Eventually, United grew so sick of Real's advances that they reported the matter to FIFA, although the world governing body subsequently rejected it.
With 42 goals to his name and a world player of the year award much anticipated following United's Champions League triumph, it is little wonder the Red Devils want Ronaldo to stay.
Both Ferguson and chief executive David Gill have insisted the winger is not for sale at any price and while it has been viewed with growing certainty Ronaldo would eventually get his 'dream' move to Real, there have been suggestions in the last couple of days he has decided to stay where he is.
No matter what his future holds, United will want to make sure Ronaldo receives the best treatment possible for his injury.
The player has an impressive appearance record since his move from Sporting Lisbon in 2003, since when he has rarely been injured and United will hope to have Ronaldo available when they begin the start of their Premier League title defence against Newcastle on August 16.
Ronaldo refused to comment on his future when he returned to Portugal after a break in Italy on Wednesday night.
'I can only say that (I) will spend the period of my recovery in my house in Sintra, but regarding my future I cannot say anything,' Ronaldo said in Portuguese newspaper A Bolo.