It had been a little more than a month since

increased his work load in his

, the Trail Blazers having cleared their once-prized center for "basketball-related activities" on the court.

According to acting general manager Chad Buchanan, there were some good days. And there were some bad days.

But those bad days became enough of a concern that the Blazers recently scheduled a magnetic resonance imaging test on both of his knees, which once again revealed bad news: Oden needed knee surgery. Again.

Only this time, it was on his right knee, not the knee that was recovering from a fractured patella and microfracture surgery.

Oden had arthroscopic surgery Friday in Vail, Colo., to clear debris from his right knee, a minor procedure, but Buchanan said his left knee might also have to be operated on in the next week. Buchanan also said a small blood clot near Oden's left ankle was discovered in the pre-operation exam, but the clot has been treated and is of no concern.

The Blazers would not say Oden is done for the season, saying only that he remains out "indefinitely." But with roughly 2 1/2 months left in the season, the 24-year-old once again looks closer to missing an entire season than he does to making a comeback.

"That would be speculation at this point," Buchanan said about Oden missing the season. "We are going to continue to stand by and support Greg and listen to what the doctors have to say."

This is the fourth

for Oden since he was the No. 1 overall pick in the 2007 draft. This is his fifth NBA season, but he has played in only two -- recording 61 games in 2008-2009 and then 21 games in 2009-2010. Only one of his surgeries -- a 2009 fractured left patella -- was the result of an acute injury that happened while playing basketball.

The right knee has not given Oden problems since 2007, when he had microfracture performed before the season started.

His left knee was the knee in question during his December visit in Vail, Colo., when the team deemed he had suffered a setback because of an issue with a non-weight bearing ligament in his knee. The left knee was chipped in February of 2009 when he collided with Corey Maggette in a game at Golden State, forcing him to miss 14 games. The next season, he fractured his left patella in a December home game against Houston when he jumped to block a shot by Aaron Brooks, ending a season in which he was one of the team's best players.

He has never returned to the court since that game, having undergone microfracture surgery on his left knee in November of 2010.

The team had hoped he would return this season, and extended an $8.9 million qualifying offer, which Oden accepted. However, after an exam in Colorado on the eve of training camp, the team deemed he had suffered a setback, and the Blazers and Oden's representatives negotiated a reduced salary, reported to be around $1.5 million for this season.

In his career, the 7-foot, 270-pound Oden has played in 82 games, the equivalent of one NBA season. Oden has career averages of 9.4 points and 7.3 rebounds.