Olympic gold medal gymnast McKayla Maroney fell while performing on a national gymnastics tour and will undergo tests to see the extent of the injury.
Maroney and the other members of the so-called Fierce Five will be in San Diego Thursday as the next stop on their 40-city post-Olympics tour.
Aly Raisman also suffered bruised knees after a fall on the uneven bars Sunday night but is not expected to miss any shows.
Maroney hurt her left knee, and was having additional tests Monday according to the Associated Press.
Raisman, Maroney earned gold at the London Games along with teammates Gabby Douglas, Kyla Ross and Jordyn Wieber.
It was the first Olympic title for the U.S. women since 1996.
Raisman added a second gold on floor exercise, while Maroney won silver on vault.