Kelly Clarkson suffered a permanent knee injury whilst trying to lose weight during the early days of her career.

The 35-year-old singer was propelled into the spotlight after the release of her sophomore album 'Breakaway' in 2004, and has admitted the pressure to keep herself looking thin made her exercise so much that she caused permanent damage to her meniscus, which is the cartilage found within the knee.

She said: ''Any time you saw me thin, honest to God, the reason is because I lived on a treadmill and I'd put my in-ears in so people would stop talking to me, because I was so tired.

''Especially those 'Breakaway' days, I was tired. I was always surrounded by people, I never had a minute alone. So my minute alone was on a treadmill and I wrecked my meniscus 'cause of that.''

Nowadays, the 'Piece By Piece' singer - who is stepmother to Savannah, 16, and 11-year-old Seth, and has River, three, and 19-month-old Remington with husband Brandon Blackstock - is happy with her weight, and doesn't strive to be thin for the sake of her career.

Speaking to The Sun newspaper's Bizarre Life podcast, she said: ''I'm a singer. We're not models. I don't see my life as a struggle. I just see me living my life. Sometimes you're thin, sometimes you're thicker. Sometimes you're happy, sometimes you aren't as happy. Success doesn't always equal happiness. Now success is happiness so it's nice.''

Kelly's comments come after she previously insisted that her curvy figure is a sign of her happiness.

She said: ''It's when I'm fat that I'm happy. People think, 'Oh, there's something wrong with her. She's putting on weight.' I'm like, 'Oh, no! I'm sorry, but that represents happiness in my emotional world.' For me, when I'm skinny is usually when I'm not doing well.''