Melissa Gilbert
was mysteriously M.I.A. at the end of last night's "Dancing with the Stars" -- and now we know what happened to her!

"If you're wondering why Melissa and Maks are not here, she injured herself," host Tom Bergeron cryptically explained at the end of the episode. "And as a precaution, has gone to the hospital to get it checked out."

But Melissa explained further, via Twitter, what really happened.

"I'm alright. Mild concussion and whiplash. Very soon I will be safely home resting and being taken care of."

And it even sounds like Gavin DeGraw helped get her to the ambulance, as she also tweeted "@GavinDeGraw bless your heart for carrying me down those stairs!"

Expect a full explanation tonight during the results show.

Check out her and Maksim's paso doble above ... we don't see any sign of injury, do you?

Hot Videos