Gibson (knee) underwent surgery Thursday to address a fracture in his foot, John Keim of ESPN.com reports.
Gibson played through the fracture for most of December but then missed the final two games of the regular season after spraining his knee Week 16. He's expected to recover in time for offseason workouts, at which point he'll be in the fourth and final season of his rookie contract. Rookie back Brian Robinson, meanwhile, will miss Week 18 with a knee injury that isn't considered especially serious. Jonathan Williams and Jaret Patterson are Washington's healthy backs for the season finale, while Robinson and Gibson should be ready to go for OTAs.