The message came at a press conference on Monday. The 23-year-old injured himself on Sunday when he was training pole vault.
Rooth missed the mat in the landing, got an overstretch in the knee and hit his elbow.
The first thing I thought was that the mat was a bit far away, says Rooth.
Now an operation is pending.
It's not something I'm looking forward to. I've never been operated on before, so I didn't have the best sleep of my life tonight. It's not a fun situation to be in.
When Rooth won Olympic Games gold in Paris last year, it was a surprise, but since then the star has been plagued by major injury concerns and has barely been able to compete. The 23-year-old missed the entire indoor season and has not participated in a decathlon competition during the summer either.
Rooth was considered one of Norway's medal hopes in the World Championship.
