Enable will be out of action until August at the earliest after suffering a setback, connections have anounced.
John Gosden's brilliant filly enjoyed a fantastic campaign in 2017, winning six of her seven starts including five consecutive Group One triumphs.
She has not been seen on a racecourse since claiming Prix de l'Arc de Triomphe glory at Chantilly last October, but had been pencilled in to make her reappearance in the Coronation Cup at Epsom on 1 June.
However, she will now miss the first part of the season through injury.
Teddy Grimthorpe, racing manager to owner Khalid Abdullah, said in a statement: "Enable has met with a setback in training. She has some filling in her knee which is being fully investigated."
Connections are hopeful Enable will run again before defending her Arc crown in Paris.
Grimthorpe added: "The advice that we have is, that given reasonable circumstances, she should be ready to run in August as a preparation for the Prix de l'Arc de Triomphe."