Madsen was injured on March 15 against Dallas and hasn't played in the last three games. He also missed 24 games earlier this season with a broken left thumb.
"(Trainer) Gregg Farnam, Kevin McHale and I had a lot of talks about trying to play the rest of the season," said Madsen, who is averaging 2.1 points and 3.1 rebounds this season. "But we thought about the risks of that and that we have a healthy Ervin Johnson and it was a no-brainer."
Madsen plans on having surgery sometime next week and expects to take about three months to recover.