Novak Djokovic withdraws from the French Open with a knee injury and will lose the No. 1 ranking

Novak Djokovic has withdrawn from the French Open due to a knee injury sustained during a fourth-round victory. This decision forces him to relinquish his title defense and his number one ranking. An MRI confirmed the severity of the injury. Djokovic was scheduled to face Casper Rude in the quarterfinals.

In which round did Djokovic hurt his knee?

What did the MRI reveal about Djokovic's injury?