Jane Fonda admits that she is "not immune to age".

The glamorous 73-year-old actress, author and fitness guru seems to defy the ageing process.

Although Jane is physically fit, the actress reveals that she is afflicted by age-related maladies.

"I am not a freak of nature and I'm not immune to age. My body is slim because I have good genes. My dad was long and lanky and my brother is too. But the truth is I suffer from osteoarthritis and it's really hard," Jane told British newspaper the Mirror.

"I've had a hip replacement and a knee replacement and my bones are fragile because I suffered from bulimia for a long time as a young woman."

Jane is currently promoting her 27th workout video.

Although she can't perform routines that are physically strenuous anymore, the star believes that exercise is key in maintaining good health.

"When you're older exercise is the number one thing you need to do to age successfully," Jane said.

"Sure, I wish I could still run and jump up and down, but I can't. Instead I do what I can do now, knowing I can do it safely and without harming myself."

Jane's osteoarthritis has led to painful broken bones in areas around her body.

The discomfort from the malady that she experiences does not get her down.

Jane is proud of how healthy she is in her 70s.

"I have to admit when I filmed this latest workout I was a little worried because I know I look better than normal for someone my age and I didn't want that to intimidate anyone. But what's been really exciting is finding that I give people hope they're not as scared of getting older when they see me," she said.

Jane's video Trim, Tone and Flex will be available in stores around Christmas time.