The 33-year-old right-back, who only recently returned from a long-term ACL injury, sustained the new issue in the same knee during Real Madrid's 2–1 victory over Barcelona in El Clasico on Sunday.
A club statement confirmed the severity of the problem after medical tests were carried out on Monday.
"After the tests carried out on our captain Dani Carvajal by the Real Madrid medical services, he has been diagnosed with the presence of a joint free body in his right knee. Carvajal will undergo an arthroscopy," the statement read.
Spanish outlet El Partidazo de COPE reported that the veteran defender is expected to miss between two and three months of action, ruling him out for the remainder of 2025. A possible return is now being targeted for early 2026.
Carvajal's latest setback is particularly frustrating as it comes shortly after his comeback from a string of injuries that limited him to just seven appearances this season.
He featured in Real Madrid's FIFA Club World Cup semi-final against Paris Saint-Germain before suffering a muscle problem that kept him out for several weeks.
He made his return as a substitute in El Clasico, where he was involved in a post-match incident with Barcelona youngster Lamine Yamal.
Carvajal, who has spent over a decade with Los Blancos and captained them since 2025, will now focus on rehabilitation as Real Madrid continue their pursuit of domestic and European honours without one of their most experienced leaders.
Jose Mourinho has praised Real Madrid's squad depth after their 4-1 Champions League win over RB Leipzig but insisted his team must improve before Sunday's El Clásico against FC Barcelona.
Barcelona midfielder Dani Olmo will miss Sunday's El Clasico against Real Madrid after suffering a thigh injury during Tuesday's 4-2 Champions League defeat by Paris Saint-Germain.
Real Madrid secured their third consecutive Champions League victory against Leipzig at the Bernabeu on Wednesday night.
Liverpool defeated Villarreal 4-3 in their UEFA Champions League encounter at Anfield on Tuesday evening to maintain their perfect record in the tournament.
