LACHIE Henderson's pre-season has hit a new hurdle with the Geelong defender undergoing a second bout of knee surgery in as many months. 

The 27-year-old had an arthroscope on his right knee on Tuesday after being plagued by soreness since his original October operation. 

Henderson told AFL.com.au last week his initial surgery was to repair "wear and tear" that had accumulated across his 10-year career. 

But the Cats said on Wednesday he had suffered a setback, having been restricted by mild pain ever since, and the decision to investigate a second surgical repair was made earlier this week.  

He was planning to return to full training in January, but will now start a modified training program over the Christmas break. 

"While this is a setback for Lachie, it will allow him to move forward on a rehabilitation plan," Cats football manager Simon Lloyd said.

"Lachie will work closely with our medical team over Christmas with the aim to return to football early in the new year."

Henderson had not been cleared to take part in football drills leading up to the second operation, but had been running freely and maintaining his fitness base.  

Last week, he was confident the knee issue wouldn't impact his preparation for next season dramatically. 

"It was a bit of wear and tear. It wasn't really a set injury, it's just a bit of wear and tear over the 10 years I've been playing," Henderson told AFL.com.au.

"Nothing too serious but I've just got to work through it."