Miley Cyrus Says Her Kneecap Started to 'Disintegrate' Due to Infection

Miley Cyrus' recent infection was like a wrecking ball to her knee ... 'cause she caught something that started to "disintegrate" the area -- after rolling around the Hollywood Walk of Fame.

The singer-songwriter appeared on "Jimmy Kimmel Live!" Thursday night to talk about her upcoming album and accompanying film "Something Beautiful" ... and, Jimmy joked Miley's lucky she wasn't stabbed by a loose needle while rolling around on Hollywood Boulevard.

Cyrus says she didn't end up with a needle to the eye ... but, a few weeks after the shoot, she ended up in the ICU -- mainly because of a space issue instead of the serious nature of the infection.

Miley claims the doctor was shocked at the seriousness of the infection ... and, he asked her if she had any idea how she could end up with such a bad contamination.

MC says she came clean about her dirty act ... and, her doctor responded in the most relatable fashion -- watch the clip to the end to hear what he said.

We don't know for certain which song landed Miley on the street ... though she does have a track titled "Walk of Fame" -- so, if we had to make an educated guess, that's not a bad one.

The "Something Beautiful" album comes out May 30, with the accompanying film set for premiere on June 6.