Michael J. Fox Falls Into Couch During 'BTTF' Panel, Plays It Off

Michael J. Fox says his battle with Parkinson's disease is getting worse ... and that seemed evident during a 'Back to the Future' event this weekend where he took a fall, but still played it off pretty well.

The beloved actor was on hand Sunday for a 'BTTF' fan expo in Philly ... where fellow costars Christopher Lloyd and Tom Wilson (Biff) also joined him. Michael had just been intro'd and was walking out in front of the crowd and bowing down to Tom, before making his way to a sofa on the stage.

That's when MJF stumbled forward ... luckily, falling headfirst into the sofa cushions.

Of course, it was a jarring sight, and audience members were shocked and clearly concerned. But, a second later, Mike popped up with a ton of energy -- and didn't seem phased by it at all. When it was clear he was okay, the tension loosened up.

Michael recently revealed he falls kinda regularly now ... he spoke at length about it recently with CBS, and they actually aired footage of him nosediving on the streets of NYC. He says Parkinson's is hindering him more and more each day.

It was pretty sad ... MJF said he didn't think he'd live past 80 due to his Parkinson's, but despite this reality, he keeps putting on a brave face and keeping a good attitude.