Michael J Fox falls on stage as he admits he is suffering 'intense pain' from Parkinson's

Watch: Michael J. Fox stumbles and falls on stage at fan event

Michael J. Fox suffered a fall at a fan event after losing his footing as he walked onto the stage.

The 61-year-old actor was being introduced at the Back To The Future expo at the Pennsylvania Convention Center in Philadelphia to rapturous applause from the audience, when he tripped on stage and stumbled sideways onto a sofa.

There were gasps from the crowd, but Fox quickly leapt up to show fans he was okay and brushed off the incident.

Read more: When was Michael J Fox diagnosed with Parkinson’s disease?

The Marty McFly star was diagnosed with Parkinson's disease – a neurological condition that affects body movement – in 1991, when he was just 29.

Speaking about his condition he told fans: “I’m in pain, intense pain.”

Fox joined Back To The Future co-stars Christopher Lloyd, 84, and Tom Wilson, 64, at the event, who played scientist Emmett 'Doc' Brown and high school bully Biff Tannen in the 1985 cult hit time travelling adventure which went on to become a trilogy.

Fox - who has four children with his wife Tracy Pollan - recently told Lorraine how laughing with his family helped him cope with the difficulties of his condition.

He said: "I’m more happy than not.

"And I think it helps to be silly. I think you’ve got to be silly sometimes in the face of things that are really daunting and threatening.”

Fox told CBS in April that living with Parkinson's was becoming increasingly hard.

He admitted: “I’m not gonna lie. It’s getting hard, it’s getting harder. It’s getting tougher. Every day it’s tougher.”

According to the NHS website, Parkinson’s is a condition in which parts of the brain become progressively damaged over many years. Symptoms include involuntary shaking of particular parts of the body, slow movement and stiff and inflexible muscles.

Fox set up a foundation in his name in 2000 to help fund research to find a cure for Parkinson's. It has raised £1.2billion to date.

Read more: Michael J. Fox says he doesn’t expect a Parkinson’s cure in his lifetime

Fox said: “This will crack wide open our ability to develop next-generation drugs that will benefit everyone who is living with the disease. We are standing on the threshold of being able to prevent it altogether.”