Mayor Thomas Menino will undergo surgery on his right knee Tuesday afternoon to repair a partially torn tendon. A year ago, Menino had surgery to address a total tear in a tendon in his left knee. At a City Hall press conference with his doctor, Thomas Thornhill, the head of orthopedic surgery at Brigham and Women's Hospital, Menino said he expects to be active again by Monday, but Thornhill said that depends on his rehabilitation. "If he's able to do it, he will do it," Thornhill said. Menino said he was not in any pain and described the surgery as elective. "This is an annoyance," he said. "That's all it is." Thornhill performed surgery on Menino's left knee last year for a complete tendon tear.