Alexander-Arnold encountered the issue in the warm up. But he was still able to go ahead and play the full 90 minutes on the south coast and manager Jurgen Klopp had expressed hope afterwards that it would be nothing too serious.
The 20-year-old academy graduate had only just returned from a spell out of the side before Christmas after recovering from a foot problem. Liverpool have since also loane back-up right-back Nathaniel Clyne to Bournemouth and squad depth will now be tested more than ever.
Dejan Lovren's absence forced Klopp to use defensive midfielder Fabinho in the centre of defence alongside Virgil van Dijk against Brighton. It was, however, a boost to see Joel Matip back on the bench after his recent absence and the Cameroon international could be called upon next weekend as Lovren is not expected to return until the end of the month.
It may be that Fabinho is the preferred option to replace Alexander-Arnold as the Brazilian operated as a right-back earlier in his career. Versatile cult hero James Milner is also an option.
There is also an injury concern over midfielder Georginio Wijnaldum, who also suffered a knee problem in Brighton. He is currently considered a doubt to face Crystal Palace, potentially handing an opportunity to Naby Keita to start.