De Minaur was leading 6-4, 3-2 with a break of serve when Hurkacz pulled out while down 40-0 in the sixth game of the second set, after showing mobility problems.
The result continued a strong turnaround for the 27-year-old Australian, whose tournament looked in doubt 24 hours earlier. In his quarter-final on Sunday against Russia's Andrey Rublev, de Minaur won only one game in the first set before fighting back to win 1-6, 6-2, 6-3.
Monday's semi-final began with de Minaur breaking Hurkacz in his opening two service games to lead 4-0, and again for 5-1. Hurkacz steadied, breaking back from deuce in the eighth game and holding to make it 5-4, but de Minaur held serve to take the first set.
Another break in the third game of the second set helped de Minaur build a 3-1 lead. Hurkacz fought to hold serve in the following game, surviving four break points in a marathon deuce game, to make it 3-2. But the Pole then conceded the match due to injury, giving de Minaur victory.
De Minaur will face the winner of the other semi-final between sixth seed Novak Djokovic and third-seeded Daniil Medvedev in Tuesday's final.