LATROBE - Pittsburgh Steelers linebacker Joey Porter underwent surgery to remove loose cartilage from his knee Wednesday afternoon and is expected to miss four weeks.

If Porter sits out for the full four weeks, he'll miss the Steelers' four preseason games, but will be back in time for Pittsburgh's Sept. 11 season opener against the Tennessee Titans at Heinz Field.

"We expect to have him for the opener," coach Bill Cowher said.

Porter, 28, injured the knee Tuesday during a one-on-one pass-rush drill with rookie offensive tackle Ulish Booker. Porter's knee became swollen that night and he underwent an MRI examination Wednesday morning.