They are the fashionable sheepskin boots adored by celebrities such as Coleen Rooney and Myleene Klass.
But Ugg-type footwear may be putting women at risk of serious knee problems that could even require surgery, according to a leading doctor.
Orthopaedic surgeon Ian McDermott said the boots could cause a 'knock-kneed' stance and lead to premature wear and tear of the joint because they offer insufficient foot support, the Daily Mail reported.
This triggers a poor stance, affecting the intricate set up of the knee - and if it is left long enough, can lead to cartilage damage.
Mr McDermott, a consultant at the private London Bridge Hospital, said: "If you have somebody who has severe cartilage damage at the front of their knee, and their patella is misaligned, you might have to realign the patella.
