The Edinburgh and Scotland medical teams reviewed the results yesterday and were forced to deliver what is a substantial blow to Rob Moffat's men.
"Phil sustained the injury in non-contact training. His rehabilitation starts now," said Scotland team doctor James Robson.
"He will have to undergo surgery in due course to repair the knee ligaments but the Edinburgh and Scotland medical teams will be working to deliver him ready to be considered for selection for the Rugby World Cup squad next year.
"There are many examples of players returning to full international duty having sustained this kind of injury. From our own national squad, Jason White and Nathan Hines have both recovered to play a full part in international rugby after ACL damage."
Godman, who won his 23rd and most recent international cap in last season's Calcutta Cup draw against England, will miss the entire Pool stage of the Heineken Cup but could possibly feature in the knock-out rounds if Edinburgh qualify from Pool 1.
A trip to Cardiff is first up in this year's European competition for the Scottish side as they take on the Blues on Saturday, October 9, before welcoming former European Champions Northampton Saints to Murrayfield a week later.
"It's desperately bad luck for Phil who has just played his 100th Magners League game for the club and is a key player for us. Clearly, we wish him a speedy recovery," added Edinburgh head coach Rob Moffat.