"Oklahoma!!!! I love you so much! I'm sorry for no encore. I had my jaw pop out of place & I can't hear out of my left ear. #tmjsucks," Rimes tweeted after the show.
Rimes, 31, suffers from TMJ, or temporomandibular joint disorder, which causes problems with the joints connecting the lower jaw to the skull.
"Had it since I was 16," Rimes told a fan after the show.
She also blogged about the disorder in 2012, when she wrote that she had been "living in a dental nightmare for 10 months."