Carlos Hyde suffered a torn MCL in the 49ers' Week 16 win over the Rams.
Hyde suffered the injury when he was hit in the left leg on a carry. Hyde walked off the field under his own power but did not return.
"It didn't feel that bad when it first happened. It's pain, there's some pain, but it didn't feel like bad pain. I've felt worse," Hyde said after Saturday's win. "That's why I was able to get up and walk off on my own."
Hyde nearly rushed for 1,000 yards this season to go with six touchdowns.