Khawaja was fielding at mid-off when he dived to his left to stop a ball that had been driven firmly by Jeevan Mendis of the bowling of Steven Smith. The ball appeared to strike Khawaja directly on his left kneecap and he immediately called for the medical staff before limping heavily back to the dressing room.
A CA spokesperson later said Khawaja hadn't suffered any major damage, and expected that he would be fit to bat during Australia's chase.
Khawaja has had ongoing issues with his left knee. In 2014 he required reconstructive surgery after tearing his left anterior cruciate ligament and then in October 2018 he suffered a meniscal tear when he twisted his left knee during a warm-up fielding drill during Australia's Test series against Pakistan in the UAE.
Australia have been rotating Khawaja, David Warner and Shaun Marsh in their World Cup warm-up matches, as they attempt to settle on their best batting line-up. Warner was left out of the team against Sri Lanka, amid reports that he had complained of tightness or soreness to his upper leg.
Warner's absence during the year-long ban for his involvement in the Newlands ball-tampering scandal allowed Khawaja to cement his place at the top of the order, forming a formidable opening partnership with captain Aaron Finch. Warner's return, alongside that of Smith in the middle order, has left selectors with something of a conundrum as they try to fit in a number of batsmen who have been performing at their best while opening the batting.
Australia play their first World Cup game against Afghanistan in Bristol on Saturday.