Westbrook was hurt during the first half of the Thunder's game against the Los Angeles Clippers on Thursday.
After further tests, he had surgery at the Cleveland Clinic in Ohio.
Thunder general manager Sam Presti said Westbrook will be further evaluated in four weeks before his status will be updated.
Westbrook scored 38 points in Wednesday's season opener against Portland.
The Thunder were already without reigning NBA Most Valuable Player Kevin Durant, who had surgery to repair a broken foot before the start of the season.
source: www.abs-cbnnews.com
