George struggled with multiple shoulder issues since at least February 26 and had a procedure to fix a partially torn tendon in his right arm today.
Westbrook played the final six weeks of the season with the injury to the fourth metacarpal of his non-shooting hand, sources said.
George initially missed three games with his right shoulder at the time but promptly injured his left shoulder upon his return in early March.
Before that, he was considered among the leading candidates for the league MVP award and the Thunder were one of the top teams in the Western Conference.
George also will have surgery on a small labrum tear in his left shoulder in the coming weeks, the team said in a statement.
George meanwhile averaged career highs in points (28), rebounds (8.2), assists (4.1) and steals (2.21).
"I think it came at a bad time, especially [because] the team was rolling", George said during his season-ending news conference. "I think it came at a awful time, especially the team was rolling". This season Westbrook led the league in assists for the second-straight season, making him the first player to ever lead the league in scoring twice (2015, 2017) and assists twice (2018, 2019). "We were playing good". But again, I've never made no excuses on it. It just got worse and worse as it went on. He was often seen with his finger heavily taped toward the end of the season.
On April 25, George said he could leave the injury alone and it would become a recurring issue, but he wanted to address it now so he could "clean up what needs to be cleaned up, so it doesn't come back". "I'd had no other thought in my mind but to be out there and play and ride it out with my guys".
The surgeries are not expected to impact his offseason training.