Jones said he aggravated a previous knee injury in Sunday's win over the Cardinals, Ian Rapoport of NFL Network reports.
Jones said he dealt with a sprained PCL over the summer and aggravated it in the second half of Sunday's victory. Jones was able to stay in the game and finish the contest with a knee brace. With Brock Purdy (shoulder/toe) nearing a return, potentially as soon as Week 4 against the Jaguars, Jones may get time to heal. Adrian Martinez is next up on the depth chart as the Niners' QB3.