Keira Knightley caught pleurisy through over working.

The 'A Dangerous Method' actress was struck by the lung problem last year - characterised by a pain when sufferers breathe - but at the time thought she had just hurt one of her ribs.

She said: ''You do period films and you get some sort of weird archaic disease.

''And I didn't realise, so I went on for another month. I just stupidly never went to a doctor.

''I was rehearsing for this play and then I found in rehearsals it got so bad that I couldn't stand up any more.''

''And they said: 'Please, can you go to the doctor?' ''

The 27-year-old star has since turned to yoga to help keep her limber and functioning, but that has also resulted in a few injuries.

She told the Australian edition of Harper's Bazaar magazine: ''My body at the end of last year was breaking and I thought, 'I've really got to try and do something'.

''I've been trying to get myself into gear. I've been doing yoga, but I've already got ­injuries - from f***ing yoga.''

Keira's most recent role was in an adaptation of Leo Tolstoy's epic novel 'Anna Karenina', in which she played the lead, a role which she described as the ''hardest thing I have done to date,'' leaving her glad to let off some steam in the bar afterward.

She added: ''I'm s**t at karaoke, but on occasion [I like] a bit of karaoke. A good dance is necessary as well. Gin makes me cry though; I'm a vodka girl.''