Wales star out for the season
The flank left the field during the first half at Rodney Parade and will now miss the remainder of the season.
"After speaking to consultants and seeking specialist opinion, the decision has been taken in Dan's [Lydiate] best interests to undergo surgery," Chris Towers, Ospreys Medical Performance Manager, confirmed.
"That process will take place this week, ruling him out of consideration for the rest of the current season."
The news is not only a big blow for Ospreys but for Wales as well with the upcoming Six Nations tournament just around the corner.
Wales begin their Six Nations campaign against Scotland in Cardiff on February 3.