Valdes landed awkwardly when making a save from a routine free-kick during the first half of Barca's 3-0 Liga win over Celta Vigo on Wednesday.
The 32-year-old has since been diagnosed with a tear of the anterior cruciate ligament in his right knee, an injury that ends his hopes of competing in the FIFA World Cup in June.
The news also marks a sad end to Valdes' Barca career, having previously revealed that he will leave when his contract expires at the end of the season.
Valdes has made a significant impact during his time with the Catalan club, playing over 500 times and winning six La Liga titles and the UEFA Champions League three times.
And Valdes has been quick to receive sympathy from his team-mates at club and international level via Twitter.
Javier Mascherano posted: "Nothing to celebrate. Get well soon @1victorvaldes."
Cesc Fabregas: "Good win but sad about @1victorvaldes's injury. Hope you recover soon. We are all with you!"
Jose Pinto: "Very sad for what happened with my teammate and friend @1victorvaldes I hope with all my heart that it's not really bad.
Spain team-mate Pepe Reina: "Sad news! Lots of strength to my friend @1victorvaldes! You'll soon be giving goalkeeping lessons again, genius."
