The classy fullback has been ruled out of Super Rugby for six weeks.
He injured an ankle in the game against Moana Pasifika last Friday that ended in bizarre scenes after a power cut took out a light tower and stopped the television broadcast.
Scans had since revealed an issue that required six weeks on the sidelines, the Highlanders announced.
Ratumaitavuki-Kneepkens started all seven games of the season behind wingers Caleb Tangitau and Jona Nareki.
The personable custodian was second in the Highlanders for both carries (64) and metres gained (388), and his 24 defenders beaten were fifth in Super Rugby.
Ratumaitavuki-Kneepkens started the Highlanders’ final seven games last year after making a miraculous return from a broken neck.
Sam Gilbert was the regular No 15 earlier in the season, and he now plays in Ireland.
The Highlanders have several options to replace their main man at the back.
Injury-plagued dynamo Finn Hurley made his comeback in club rugby on Thursday night and might be rushed straight back in to make a ninth appearance for the Highlanders.
Young Wellington utility Stanley Solomon — waiting for his debut — and seasoned Canterbury utility Andrew Knewstubb are other options, while Reesjan Pasitoa and forgotten man Taine Robinson could also be considered.
