Green has already shed his walking boot and he's running on a zero-gravity treadmill, according to Geoff Hobson of Bengals.com. However, he's still taking a cautious approach.
"Just making sure I don't come back too soon and hurt it again," said Green.
The wideout has struggled to stay on the field in recent years, missing seven games because of a toe issue last season and another six due to a hamstring tear in 2016.
When Green is healthy, few can match his talent and output. Since entering the league, the now 31-year-old has put up the fourth-most receiving yards, caught the fifth-most passes, and scored the sixth-most receiving touchdowns in the NFL despite missing those 13 games over the past few seasons.