The `Marry The Night` singer was forced to cancel the remaining dates of her `Born This Way Ball` tour earlier this year after suffering a labral tear on her right hip, which required an operation and left her wheelchair-bound.
The 27-year-old singer surprised the crowd at jazz singer Brian Newman`s gig at the Rose Bar in Gramercy Park Hotel, New York, last Thursday (09.05.13) by joining him on stage for a rendition of his track `Watch Over Me`.
Newman was thrilled to perform with Gaga and took to his Twitter page to share his excitement.
He tweeted: "Thanks to the 1&only @ladygaga for coming out to @GPHhotel tonight an singing a song!! @tommylondon @angiepontani @mrmartye @thedirtypearls. (sic)"
Gaga has been on the road to recovery since being spotted out for dinner with her boyfriend, `The Vampire Diaries` actor Taylor Kinney, in Chicago last month.
The generous pop superstar has also agreed to provide the funds for a fan who requires a similar operation to her own.
Emma C, 19, was overwhelmed when the Gaga "reached out" to her after hearing about her battle with scoliosis and hip dysplasia.
She wrote online: "Gaga reached out to me and is hooking me up with her team that did her surgery in NYC as I have been needing a hip replacement for quite some time.
"We`re planning on flying out this weekend, all expenses paid, for a consult. The gesture is absolutely incredible ... I broke down sobbing. Words can`t describe how incredibly Blessed I am."