Vaughan faced just one ball before sinking to the ground in pain as he made his ground at the non-striker's end and then limping off the pitch following several minutes' treatment at the crease on day two against Pakistan A.
He came in at number three after the loss of opener Marcus Trescothick for just one run in a second-innings effort which was worth 194 for five by tea, thanks principally to a century stand between Paul Collingwood (61) and Andrew Strauss (56).
By then it had been confirmed the captain, leg heavily iced and strapped, was having the near inevitable scan on his injury.
His participation in the first Test, set to begin in Multan on Saturday, was therefore in obvious doubt until the outcome of his hospital visit was known.
It was a similar problem with the same knee which struck Vaughan down in the Lord's nets last year and ruled him out of the first Test against New Zealand, for which Trescothick took over as captain.
This time, Vaughan's discomfort followed the early elimination of Trescothick who was pinned lbw on the front-foot defence by Mohammad Asif - on his way back before his team could rub off a marginal first-innings deficit.
Vaughan was replaced by Kevin Pietersen, who also went lbw to Asif - for a first-ball duck which took his personal tally from four innings on tour to just 16 runs and left him as the only top-order batsman still without a significant innings under his belt.
England recovered from 10 for two, courtesy of Collingwood and Strauss only for the third-wicket pair to depart within an over of one another - in keeping with a tour which has so often seen wickets fall in damaging clusters.
Before lunch, Strauss escaped a sharp chance at gully on eight when a substitute fielder failed to hang on - and Collingwood went from 15 to 21 with a hooked six 'caught' by Asif who ran over the boundary in doing so. Shahid Nazir was the unlucky bowler both times.
In early afternoon, however, Strauss and Collingwood produced easily England's most convincing passage of play so far on tour in a stand worth 113 runs.
The opener was first to his half-century, having hit six fours from 93 balls. But Collingwood batted at a much quicker tempo as he inked his name in for the first Test with a 58-ball 50 completed by his third and fourth sixes, to go with the same number of fours.
There was an encouraging confidence as they dealt with the spin of Arshad Khan and Mansoor Amjad; then when Asif returned Collingwood tucked in again.
It was Asif, though, who broke the partnership - Strauss cutting at a wide delivery and adjudged caught behind.
Then before new batsman Andrew Flintoff could make himself at home, Collingwood did not time a big hit at Amjad and was well-caught by Nazir running in from deep backward square-leg.
A Flintoff cameo followed only for him to fall to a re-run of Collingwood's dismissal, falling victim to Amjad's leg-spin. Geraint Jones and Ashley Giles were able to see their team through to tea without further loss, although the wicketkeeper-batsman was not convincing in a scratchy innings which featured a stream of loud lbw appeals against him.
Stephen Harmison had begun the day by making short work of the hosts' last two wickets as they were bowled out for 138.
It took him just 11 deliveries to get rid of Asif, neatly caught in the slips by Trescothick, and then to intimidate number 11 Mohammad Khalil who went lbw walking across his stumps.