Ralph Macchio said via Twitter he hopes a ruptured cyst on the back of his knee doesn't keep him from performing on "Dancing with the Stars."
Each couple is to perform two routines Monday night, People.com said.
"Have missed days of rehearsal this week," Macchio said in a Twitter message Monday.
"Had a ruptured cyst on the back of my knee causing acute pain. Hoping to be able to perform tonight!"