England captain Michael Vaughan faces an anxious wait to discover whether a knee injury will rule him out of his team's tour of Pakistan almost before it has started.

Vaughan, who has a history of ligament problems in his right knee, crumpled in a heap at the crease before he had scored a run on day two of England's final warm-up match against Pakistan A at Bagh-e-Jinnah.

He required several minutes' treatment on the pitch before limping off to have his knee packed with ice and heavily strapped and then going to hospital for a scan.

England's chief medical officer Peter Gregory later confirmed that Vaughan's chances of being fit in time for the start of the first Test in Multan on Saturday are 'slim', adding that if the scan reveals a ligament tear the captain will be very likely to need an operation which would almost certainly mean the end of his tour.

"We will need 24 or 48 hours to see how he pulls up clinically and responds to the treatment, as well as to take into account what we find on those scans," said Gregory.

"I am hopeful - but whether that is realistic or not we will have to wait and see. He has a history of cartilage damage, and it would be very likely this is too.

"Usually with tears you would need an operation."

Vaughan's injury overshadowed an improved if not yet entirely convincing performance from England's batsmen as they posted a second-innings 256 all out to leave the hosts needing 245 to win.

Paul Collingwood (61) and Andrew Strauss (56) shared a third-wicket stand of 113, and Ashley Giles added a very handy 49 as he shepherded the tail.

More worryingly, Kevin Pietersen registered a first-ball duck to remain horribly short of runs after four innings on tour so far - and England lost five wickets to young leg-spinner Mansoor Amjad, hardly inspiring confidence they will be able to deal with Danish Kaneria and Mushtaq Ahmed on the expected turning pitches in the three-Test series to come.

Pakistan A raced to 31 for one in just four overs by stumps to open up the possibility of a close call for England tomorrow if they are to remain unbeaten on tour.