Britney Tripped Up by Injury Mon Mar 22, 6:30 PM ET Add Entertainment - E! Online to My Yahoo! By Sarah Hall It was her knee against the music. • News: Britney's suicidal tendencies? • News: The scent of Britney • E! Online's review of In the Zone E! Online Photo Reuters Slideshow: Britney Spears Oops! girl Britney Spears was forced to cut short an encore after her concert last Thursday in Moline, Illinois, and cancel a Friday performance in Chicago after she hurt herself during a complicated dance routine. Spears was performing a new song, "Boom Boom," when the mishap occurred, according to reports. Perhaps she hadn't worked out all the kinks in the routine--in any case, Spears was forced to abandon the stage. Several minutes later, she reappeared on the stage in a white bathrobe and apologized to her fans for cutting the performance short. The "Toxic" singer had planned to continue with two more songs, but the injury was apparently serious enough to keep her out of the zone. Spears' label, Jive Records confirmed that Spears would not be performing in Chicago as scheduled. "Due to an unfortunate knee injury Britney Spears (news) suffered towards the end of her show last night in Moline, Illinois, she will not be performing tonight at the Allstate Arena as scheduled," the company stated last week. Spears also postponed her Sunday performance in Detroit. Jive Records stated that the performances would be rescheduled sometime in April, with specific dates to be announced this week. "Britney is resting her knee and is looking forward to resuming her tour in Atlanta on Tuesday," the label stated. According to on-air personality Ryan Seacrest, Spears has been fitted with a special knee brace that she is wearing during rehearsals. Doctors will make the final decision whether she will perform Tuesday night. The pop princess is currently in the midst of her Onyx Hotel Tour with dates scheduled across North America and in Europe and Asia. Her latest CD, In the Zone, has sold over 5 million copies. Off the tour circuit, Spears recently signed with Elizabeth Arden to create a fragrance and cosmetics line. The first product--an eau de Brit--is due to land on shelves this fall.