"I feel good about getting it done now," Balfour said. "I didn't know what it was other than I was a little sore," Balfour said in the statement. Balfour said through the team that the knee bothered him late last season but wasn't considered anything serious and that the knee calmed down during the offseason. Oakland Athletics closer Grant Balfour had arthroscopic surgery on his right knee to repair a torn meniscus. Melvin said Balfour felt some knee tenderness toward the end of last season, but went about his normal offseason routine without any pain before experiencing some on Wednesday prior to his scheduled bullpen session. The operation was performed by local orthopedist Dr. Douglas Freedberg, who also operated on Scott Sizemore last spring, when the A's infielder suffered a torn ACL on the first day of workouts.