Ugg boots
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We know, it sounds like something made up by a rival, less comfy, boot manufacturer.

But, alas, it is not.

A leading orthopaedic surgeon has warned against wearing Ugg boots in the winter months, saying they lack support for the lower leg if people buy the wrong size.

And constant wear and tear of the boots can cause the heel to get worn away, which can flatten out the arch of the foot which is needed for posture support.

Both of these can lead to a bad posture, knee pain and even back pain.

Ian McDermott, a knee surgeon in London, said: "This is a bit of a 'red flag' and a sign that it's potentially worth investigating the knee with X-rays and an MRI scan to check exactly what is going on inside the joint.

"The longer these things are left, the worse the damage can become, and the harder it can then be to fix.

"Sheepskin boots and high heels may look great, but vanity may come at the cost of potential physical damage to your body.

"Unsculpted and flimsy footwear can mean that your feet aren't fixed in one location as you walk, meaning that the lower limb is working harder, with a greater risk of damage.

"Listen to your body and make sure to not wear flimsy boots every day.

"Although sheepskin boots can seem like the first choice for comfort this winter, it's sensible to opt for a sturdy pair of boots with correct arch support and greater support."

The problem with walking in shoes that don't properly support your feet is that your knees are likely to carry your weight unevenly.

"Planovalgus [flat feet] then tends to increase external rotation and valgus in the tibia, causing a knock-kneed posture," Mr McDermott added.

"This then increases what's referred to as the 'Q-angle' in the knee, meaning that more weight is put on the outer side of the knee and more strain on the inner side.

"It also exacerbates lateral patellar maltracking, which is where the kneecap rubs more on the outer side of the front of the knee, causing anterior knee pain and, eventually, increased wear and tear of the articular cartilage on the back of the kneecap."

And if you were born with existing posture problems, like naturally flat feet or hypermobile ankles - meaning the move more than normal - then you're going to be affected more.

"If someone born with an inherently poor structure or with poor alignment then wears a poorly supported pair of shoes or boots, this can exacerbate the whole issue and this can then end up being the final straw that pushes them into developing symptoms and actual orthopaedic problems," Mr McDermott said.

But it is not just Ugg boots wreaking havoc on our feet.

High heels and any poor-fitting shoes can cause posture problems.

Paul Argent, a biomechanist from chronic injury recovery programme Human Movement, said: "Footwear affects the body more than most people realise.

"Your feet are designed to absorb the force of you striking the ground when walking or running.

"Footwear can change how your body interacts with the ground, forcing you to land in a way that generates higher forces at particular joints such as the knee.

"Take notice of the shape and support your winter footwear gives you, as this can be the key to avoiding pain and injury."

UGG has been contacted for comment.