Thunder General Manager Sam Presti said the arthroscopic surgery on Westbrook's right knee went well.
The procedure came after April surgery on the same knee for a torn lateral meniscus, suffered in Game 2 of the Thunder's Western Conference quarterfinal series against Houston.
The three-time all-star is expected to be out until at least early November after the latest procedure, which was necessitated by swelling due to a loose stitch.
Presti, however, said it also showed the meniscus had healed properly.
"Russell has been incredible in his work and rehabilitation. He has been pain-free and has performed at a high level during practice, but has experienced recent swelling that had not subsided," he said.
Westbrook averaged 23.2 points, 7.4 assists, 5.2 rebounds and 1.77 steals per game last season.
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