Van Dijk's rib problem was not a secret, although Liverpool manager Jurgen Klopp said it was an issue of bruising.
The centre back suffered the injury before their Champions League victory over Paris Saint-Germain in mid-September, and it forced him off in the subsequent Premier League win over Southampton.
Koeman, though, suggested it was more serious than that after giving the defender the night off for Tuesday's friendly with Belgium and releasing him back to his club.
"Virgil has been playing with two broken ribs for weeks and has been constantly injecting to play at Liverpool in recent weeks," he said to Dutch publication 'De Telegraaf'.
"He wanted to play against Germany and you have to give that club something back now.
"He's back in Liverpool but he is ready to play for next week.
"He's taken a rest. He spoke to the manager.
"The medical staff of the Dutch national team spoke to the medical staff of Liverpool and made the decision that he was playing only the Germany game and then after back to Liverpool."