Madonna left fans devastated on Sunday when she cancelled her Lisbon tour date with just 45 minutes notice.
An email was sent to ticketholders at 7.45pm ahead of her expected appearance on stage at 8.30pm.
"We regret to inform you that Madonna is unable to perform this evening," read the email.
The pop star later took to Instagram, and shared her apologies with fans.
Alongside a video of an earlier performance, she wrote: “Thank you again Lisbon! Sorry I had to cancel tonight but I must listen to my body and rest!!”
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She added: “That white Port got me through the rest of the show! See you on Tuesday fingers crossed.”
The show is the eighth on the Madame X world tour that she has cancelled.
In November she was ordered by doctors to cancel three dates in Boston due to “overwhelming pain”.
Taking to her personal Instagram page to update her fans, Madonna asked them to “please forgive this unexpected turn of events”.
She continued: “Doing my show every night brings me so much joy and to cancel is a kind of punishment for me, but the pain I’m in right now is overwhelming and I must rest and follow doctors orders so I can come back stronger and better.”
Although the 61-year-old performer has refused to discuss her injuries, she reportedly told one audience in San Francisco she was suffering from a "torn ligament" and "a bad knee”.
The ‘Ray of Light’ singer has also shared videos on her rehearsal dates which show her wearing knee supports.
"How an injured Madame X warms up for a show," she wrote in the caption. "Very carefully."
Madonna’s world tour sees her plays several dates in smaller venues. Her Lisbon run began on 12 January. She is due to play 15 shows at the London Palladium from 27 January.