Orchard Park, NY -- (Sports Network) - The Buffalo Bills placed linebacker Angelo Crowell on injured reserve Thursday, effectively ending his season.

The move comes hours after Crowell originally announced he was going to miss Sunday's season-opener and might be out for up to four weeks after revealing to the team that he will undergo knee surgery.

Crowell decided to have the procedure to correct a persistent knee problem despite the fact that he apparently showed no ill effects while participating fully in practice Wednesday.

The option for a procedure might have come from problems Crowell has experienced in training camp the last two years, which includes discomfort and swelling in both knees. Head coach Dick Jauron estimated that the kind of surgery Crowell will have takes about 2-to-4 weeks for recovery.

Crowell is set to be an unrestricted free agent at the end of the upcoming season.

Keith Ellison is slated to take Crowell's place as the Bills open their 2008 regular season by hosting the Seattle Seahawks.

Also Thursday, middle linebacker Paul Posluszny missed practice after turning an ankle on Wednesday. He is expected to be healthy for Sunday's contest.