Image copyright Getty Images Image caption Juan Martin del Potro was only 20 when he beat Roger Federer in the 2009 US Open - in what remains the Argentine's only Grand Slam singles title to date

Juan Martin del Potro will have surgery in Miami on Monday in a bid to return from a serious knee injury.

Argentina's former US Open champion, 31, last played at Queen's Club in June where he fractured his right kneecap for a second time.

Surgery last summer failed to alleviate the pain, which has prevented normal activities, such as walking up stairs.

"We hope this is the definitive solution to eliminate the pain," said a statement on his Instagram account.

His team added: "It has not only prevented Delpo from playing tennis, but also making it difficult for him to perform daily activities."

Del Potro suffered the initial fracture of his kneecap in October 2018 in Shanghai. He made a comeback a few months later but the injury recurred when he slipped on the grass during a second-round match with Canada's Denis Shapovalov at the Fever Tree Championships last summer.

Plans to return for the European indoor season in October had to be shelved and now, after speaking to doctors in Europe, Argentina and the United States, it has been decided further surgery is necessary.

Del Potro won the US Open in 2009 and was runner-up in 2018, and has been a semi-finalist at Wimbledon and the French Open. He lost to Andy Murray in the 2016 Rio Olympics singles final before helping Argentina win the Davis Cup for the first time later in the year.

Since he made his Grand Slam debut in France in 2006, Del Potro has been forced to miss 19 of tennis' biggest events, but when fit, he has been a formidable opponent for Murray, Roger Federer, Rafael Nadal and Novak Djokovic.

No timeframe has been given for any potential return.