Michael J. Fox was participating in a "Back to the Future" panel on Sunday when he took a tumble.

Fox was at the Pennsylvania Convention Center in Philadelphia for a Q&A about the film. When he was introduced and bowed he lost his balance, falling and bumping into a couch.

Fox was diagnosed with Parkinson's disease at the age of 29 in 1991. The condition can affect a person's balance.

His costars Christopher Lloyd and Tom Wilson were also onstage.

Fox recently shared that his battle with Parkinson's has gotten more difficult. "I'm not gonna be 80," he told "CBS Sunday Morning."

He added, "I'm not gonna lie. It's gettin' hard, it's gettin' harder. It's gettin' tougher. Every day it's tougher."

In 2000, the "Family Ties" alum started the Michael J. Fox Foundation for Parkinson's Research, which has raised more than $1 billion in research funding.

His documentary, "Still: A Michael J. Fox Movie," is streaming on Apple TV+.