Following a meeting between the Yorkshire and England medical staffs on Monday, an England and Wales Cricket Board (ECB) statement Tuesday said: "It has been decided that Michael Vaughan should be referred to a specialist on Thursday for a further assessment of his injured right knee.
"A further update will be issued in due course."
Vaughan, who now looks increasingly likely to miss the rest of the English season, has not played for England since being forced home early from the tour of India in March after a recurrence of his longstanding knee problem.
The injury flared up again while the 31-year-old was playing for Yorkshire during last week's County Championship match away to Sussex at Arundel where Vaughan was unable to field for most of the game.
Afterwards, Yorkshire physio Scott McAllister said: "Michael's rehab programme seems to have suffered a setback.
"A fourth operation on his knee is a possibility but at this stage nothing has been set in stone and the situation needs to be carefully assessed."
Another attempt at keyhole surgery to clear away internal debris would sideline Vaughan for at least 10 weeks.
That would rule him out of the four-Test series against Pakistan starting next month.
But were Vaughan to have a major operation to repair a hole in the surface of his knee joint, he might be out for as long as nine months, scuppering his hopes of leading England in their defence of the Ashes in Australia later this year and at the 2007 World Cup in the Caribbean.
Vaughan, who led England to Ashes glory last year, played the last of his 64 Tests against Pakistan at Lahore in December. He has so far scored 4,595 Test runs at an average of 42.94 with 15 hundreds and a best of 197.
The England skipper is one of several senior players on the team's injury list with all-rounder Andrew Flintoff (ankle), left-arm spinner Ashley Giles, and fast bowlers Simon Jones (knee) and James Anderson (back) also ruled out of the ongoing one-day series with Sri Lanka.
"He's obviously very disappointed," said opener Marcus Trescothick, who filled in for Vaughan as captain when he was injured for the opening Test against Pakistan in Multan in November.
"It hasn't gone how he wanted it to, but there's still time for him at the moment. We'll see how it pans out, but we need him back and we'll give him as much time as we can," Trescothick also told reporters at Old Trafford here Tuesday.
Flintoff, Andrew Strauss and Trescothick have all filled in while Vaughan has been out of action and they remain the leading candidates to take over if the selectors have to pick a new permanent skipper.
But Somerset left-hander Trescothick, forced to return home from India for family reasons, did not expect the job to be coming his way again.
"I've done it in the past and if they offer me it again then I'll think about it," he said. "At the start of this summer I wouldn't have taken on the job because I wanted to get back into the team and re-establish myself after having a break at home.
"Freddie (Flintoff)'s taken over and done a decent job and now he's not around Strauss is doing it so maybe the team has moved on and the next generation is being formed."
England are 3-0 down in the five-match NatWest Series ahead of Wednesday's fourth fixture at Old Trafford.