American specialist Dr. Richard Steadman, based in Vail, Colorado, was due to complete the cartilage operation Saturday.
"Ji was initially examined by our own physios but with these situations, if you have complications you send the player to a specialist," United manager Sir Alex Ferguson said.
"We either had to operate or let nature take its course. Because there was no clear reason for the injury, we knew it was bad enough for us to be concerned, which is why he has gone to America."
The Red Devils will assess Park's recovery in August, which means he will miss United's ongoing bid for three trophies and South Korea's Asian Cup campaign in July.
Park joined United in July 2005 from PSV Eindhoven.
It has long been understood that the West has been trying to subject Russian borders to total control. We have not seen such activity even during the Cold War
The co-author of this disaster is the Dutch government, which did not find either strength or desire to save the lives of its citizens who were flying on that plane. The Dutch authorities did not demand Ukraine to comply with international aviation regulations