"Bale has been diagnosed with a sprained right knee joint," Madrid said in a statement.
"His recovery will continue to be assessed."
On-fire Bale relishing return to England
The Welsh star reportedly picked up the injury as Madrid progressed to the Champions League final against Manchester City on Wednesday.
Various Spanish media sources reported he will miss Valencia's visit to the Bernabeu, but he is expected to fully recover well before Real's final date against local rivals Atletico Madrid to come on May 28.
Bale rescues Ronaldo-less Real at Rayo
Bale has been Real's match-winner in their last two Liga games, away at Rayo Vallecano and Real Sociedad, to remain just a point behind leaders Barcelona and Atletico with two games remaining.
However, Real will be able to call on three-time World Player of the Year Cristiano Ronaldo, who missed the games against Rayo and Real Sociedad, after he returned from a thigh injury against City in midweek.
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