The pilot reported that while on the final leg of the traffic pattern at the destination airport, he applied left crosswind correction and noted that the right rudder pedal was stiff. When the main landing gear contacted the runway surface, the rudder pedal was stuck. The pilot attempted to maintain control of the airplane; however, the airplane yawed to the right and exited the runway surface. Subsequently, the left wing impacted an airport sign, which resulted in substantial damage. At the time of the accident, the pilot was landing the airplane on runway 21 with the wind from 150° at 12 knots, gusting to 23 knots. Post accident examination revealed that a plastic foreign object was stuck in the right rudder pedal. The pilot added that during the flight, he observed a plastic foreign object bouncing around the cockpit earlier in the flight but was not sure what it was.