Jackson appeared to be hurt after dropping a low screen pass and then tackled hard by a pair of San Francisco 49ers. He left for the locker room with about five minutes to go in the third quarter Sunday.
Jackson had 76 yards on 16 carries before the injury, a huge improvement over the first meeting at San Francisco in early December when he was held to 19 yards on 10 carries.
The 49ers defeated the Rams 34-27.
Information from The Associated Press was used in this report.