Stateside Britney Spears fans won't be able to check into her Onyx Hotel anytime soon. Due to a knee injury the 22-year-old suffered last week, she's been forced to scrap the entire American leg of her Onyx Hotel Tour, which was to have run from June 22 to August 15. Spears, who hurt her knee during a video shoot last week and had to undergo arthroscopic surgery, may need up to four months to recuperate, according to a statement issued by her label, Jive Records. She'll have to stay off her feet for six weeks with her knee in a hard brace, followed by eight to 12 weeks of physical rehabilitation. That'll be enough to miss visits to all 36 cities scheduled on her tour, though Jive said the singer ''hopes to revisit those cities in the future.''