The Duchess of Sussex went barefoot for a formal Māori welcoming ceremony in New Zealand on Wednesday.
Eagle-eyed royal fans spotted a small faded scar on the inside of her left foot.
Kumar Kunasingam, consultant trauma and orthopaedic surgeon for BMI Shirley Oaks hospital, says that the scar is definitely due to open bunion surgery - which can be very painful.
He saids: "It can take up to three months before patients can wear heels again."
Meghan is known for her love of Manolo Blaknik heels and has a designer shoe collection worth thousands.
It is thought she had the surgery in 2014 after suffering from bunions for four years - and getting trolled online for them.
Mr Kunasingam explained: "The joint on metatarsal [the bone above the big toe] where bunions tend to occur has many layers.
"During surgery you have to cut through all these layers to get to the bone, which is then broken, straightened and pinned.”
“A bunion is a bit like an onion. It has so many layers and both pre and post-surgery they can make you cry.”