Getty Images

The 49ers placed receiver Pierre Garcon on injured reserve, a move coach Kyle Shanahan announced Monday.

Garcon, who missed the past four games, was scheduled to undergo arthroscopic knee surgery Tuesday.

San Francisco signed safety Tyree Robinson off the Cowboys’ practice squad to take Garcon’s roster spot.

Robinson originally signed with the Cowboys as an undrafted rookie free agent on May 11 out of Oregon. He was active in each of the first two games of the season but was waived by Dallas on Sept. 18. Robinson was signed to the Cowboys’ practice squad Sept. 20.

Robinson appeared in 52 games, with 23 starts, in five years with the Ducks. He made 201 tackles, 23 passes defensed, six interceptions, four fumble recoveries and two sacks.

The 49ers also announced they signed signed tight end Marcus Lucas to the practice squad.