ZZ Top Bassist Dusty Hill Had Tough Time Performing Weeks Before Death

Here's the last time ZZ Top bassist Dusty Hill performed with the band before his death ... and you can tell something's just not right with him.

TMZ obtained this video from ZZ Top's last concert with Dusty -- July 18 at the Iroquois Amphitheater in Louisville, KY -- and he's clearly having a tough time performing in what would ultimately be his final gig.

As you can see, Dusty is playing bass as he sits down on a large speaker ... and we're told he was sitting like this for the entire show and had to be helped off the stage because he couldn't walk on his own.

A few days after this video, ZZ Top announced Dusty was heading back to Texas due to a hip issue.

A source close to Dusty tells TMZ ... things had gotten so bad recently, he had to stop touring because of a hip injury, so he went home early to recover, and that's when he died.