"Finally going to get my regenerative treatment for my missing cartilage!! I would be jumping up and down if i could after 8 months of being in pain! Wish me Luck! " she wrote.
But it was something else that had followers talking, with fans speculating Madonna had butt implants.
One fan wrote, "The most horrible butt implants EVER", while another said, "those weird butt implants make you look ridiculous".
Another said, "What the hell happened to Your a**??!!!!"
It's not the first time Madonna has been speculated to have had butt implants.
In January last year, US gossip guru Perez Hilton tweeted a video asking, "Did Madonna get butt implants????"
The queen of pop hit back at the accusations at the time, taking to Instagram with a post that read, "Desperately Seeking No Ones Approval'β¦β¦β¦β¦.. And Entitled to Free Agency Over My Body Like Everyone Else!! Thank you 2019! Its Going to Be an amazing Year!!"
Madonna's surgery news comes after she struggled through her Madame X World Tour earlier this year, as she suffered from knee and hip issues. She was seen walking with a cane and cancelled 14 shows.
The singer also claimed to have tested positive to the coronavirus, telling fans last week she has "coronavirus antibodies" β before she reportedly left home and partied with friends during lockdown.
Madonna stopped by friend and photographer Steven Klein's birthday with several of his other friends.
Telling fans she had pledged $US1.1 million toward the development of a COVID-19 vaccine, she wrote: "I'm Grateful that I can be a part of supporting Research to Find the cure for Covid -19!!"
