They're beautiful and slaves to staying slim. Alas, that's what leaves so many celebrities with . . . KNOBBLY KNEES!
A chic black mini-dress and high heels should have provided the perfect showcase for Angelina Jolie's long, lean legs.
Yet, instead of drawing admiring glances, the outfit merely highlighted the beautiful 40-year-old actress's terrifyingly bony knees, with every tendon and sinew exposed like an anatomist's drawing.
But while her figure may have sparked worried comments when she stepped out last week, she isn't the only celebrity to have such sharply protruding kneecaps.
Angelina Jolie has knobbly knees - doctors are warning the look is not just unflattering, it's also dangerous
Demi Moore, Catherine Zeta-Jones and Kate Moss have all revealed painfully bony knees. And doctors are warning that the look is not just unflattering, it's downright dangerous.
'No one is naturally that skinny,' says consultant physician Dr David Ashton. 'These women are probably existing in a state of permanent denial.'
Even worse, he points out that behind these unseemly knobbly knees is dangerously poor body composition.
'As we get older, from the late 30s onwards, we naturally lose muscle mass. This is called sarcopenia.
'It's inevitable, but can be mitigated with weight-bearing exercises, such as tennis and walking. It's vital that women do at least some or they will rapidly see diminishing muscle.'
Donna Air (left) has always been coltishly leggy. But at 36, her knees look worryingly bony. Sarah Jessica Parker's legs seem slimmer than the fringes of her dress - but the 50-year-old does not have good thigh shape
There are key muscles, in particular the vastus lateralis and vastus medialis, which run down the thigh to either side of the knee. Put bluntly, if you don't do the right exercise you'll have no muscle definition around the knees.
'Look at athletes,' says Dr Ashton. 'They have beautifully defined legs, even if they're very slender. It's muscle.'
The fact that Hollywood stars often have very low body fat only highlights the lack of muscle around the kneecaps.
'If you rely on dieting to keep you thin, by your 40s or early 50s there will be no fat padding left around the knees,' says Dr Ashton.
Kate Moss famously eschews a healthy lifestyle in favour of partying, and the 42-year-old model's scrawny knees reveal the toll it's taken on her body. Her jutting joints show low body fat and little muscle tone. Not a good look, while Caroline Stanbury looks as though she's barely aged a day since her relationship with Prince Andrew 15 years ago. But study the socialite a little more closely and her pointy knees reveal her age - 39
Presenter and model Alexa Chung, 32, is famous for her exceptionally long and skinny legs — but, in a short dress, they only serve to emphasise her protruding knees
Lack of fat also means that skin sags around the area, a problem exacerbated by sun exposure.
Long-term, there are significant health risks. 'A lack of lean muscle means you will become feeble,' says Dr Ashton.
A simple test of muscle strength is to see whether you can rise from a chair without using your hands. 'If not, your muscle mass is poor. A third of women over 50 fall into this category.'
Incredibly, Dr Ashton also believes very knobbly knees could be a sign that some skinny stars are technically obese, which means they may suffer from high cholesterol levels and insulin resistance. Lack of calcium in the diet means there may be a high risk of osteoporosis.
'Women ought to be less than 25 per cent fat,' says Dr Ashton. 'Many super-skinny celebrities will be as much as 50 per cent fat because of the lack of lean muscle mass.
'As they have no lean muscle mass, you're looking at two eggs stuck to a broomstick. It's not a good look.'
Aristocrat and model Lady Mary Charteris has the long, lean legs of a thoroughbred. Unfortunately, the 28-year-old — who is daughter of the Earl of Wemyss and granddaughter of Guinness heir Lord Moyne — also has the horsey knees to match
Model Theodora Richards — the 30-year-old daughter of Rolling Stone Keith — has seriously knobbly knees. Her apparent lack of body fat and muscle means the skin is in danger of sagging as she ages, while Catherine Zeta-Jones reveals her well-turned calves, but the sagging between thigh and knee implies she has lost some muscle mass
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