The win levelled the four-test series between the world’s two best team 1-all with two games remaining.
Knox’s effort gave her four for the match as Australia had to come back from 2-0 down in the opening quarter and 7-4 behind at halftime.
Knox scored the go-ahead goal for 11-10 just before three-quarter time but the USA levelled early in the final quarter.
A nail-biting game ensued as nothing came off for either side until Australia drew the penalty attempt and Knox silenced the capacity home crowd.
International women’s series, La Jolla, USA: Australia 12 (B Knox 4, M Rippon 3, J Santoromito 2, G Beadsworth, T Gofers, M Santoromito) USA 11. Series tied 1-1.