Steelers linebacker Joey Porter will have arthroscopic knee surgery tomorrow in Pittsburgh, a team spokesman said today.

Porter today worked out at the Steelers South Side facility but did not attend a voluntary practice session with his teammates. He had missed all four practices the Steelers have held in the past week.

Steelers spokesman Dave Lockett said he did not know if the surgery was the reason Porter has not practiced and said coach Bill Cowher would not comment.

Porter had surgery to repair loose cartilage in his left knee in August. Lockett said he did not know if the new surgery will be performed on the same knee.