The 27-year-old German, who slipped to third in the world rankings - her lowest position for 10 years - after losing to South Africa's Amanda Coetzer in the French Open quarter-finals last week, was forced to have the operation as her kneecap was irritating a tendon.
The seven-times Wimbledon champion was operated on at a private Vienna clinic by Dr Reinhard Weinstabl. The clinic is run by Willy Dungl, who recently looked after the recuperation of the former world motor racing champion Nikki Lauda following a kidney transplant.
In a statement issued yesterday Graf said: "I deeply regret that I cannot defend my title at Wimbledon this year.
"During a medical examination of my left knee on Friday, fissures were noticed in the cartilage, a small superficial fissure in the kneecap tendon as well as its shortening.
"As a result of the diagnosis, a surgical intervention on my knee was performed this morning. During the two-hour operation, the kneecap tendon and the cartilage were restored.
"When exactly I will be able to compete again is not clear. The doctors told me that with extensive physiotherapy, returning in four to six months is realistic.
The German was out of the game for three months earlier this year with another knee injury and was a fourth-round casualty at the Australian Open and complained afterwards of an infected toe.
Andrew Richardson, beaten by Tim Henman at Queen's Club yesterday, is one of 11 British players who have been given wild cards for the singles events at Wimbledon, which begins on 23 June. Mark Petchey, Chris Wilkinson, Danny Sapsford and Luke Milligan for the men's singles and Sam Smith, Shirli-Ann Siddall, Claire Taylor, Lucie Ahl, Julie Pullin and Clare Wood for the women's singles. Three more wild cards in the men's singles and two more in the women's singles have still to be announced.
Pat Cash, the 1987 Wimbledon champion from Australia, has also been given a wild card for the qualifying competition at Roehampton.Reuse content