Lillard suffered the injury on a drive to the basket during a Feb. 12 loss to the Memphis Grizzlies. He attempted a tough shot around Memphis big man Jonas Valanciunas, then landed awkwardly with about 3:22 left and didn't return.
The injury kept Lillard out of this past weekend's All-Star Game and 3-point shootout.
Lillard did not practice Thursday as the team prepares for its first game after the All-Star break. Portland has three home games before starting a three-game road trip Feb. 27.