Middleweight Rousimar Palhares said Friday a knee injury forced him out of UFC 150 on Aug. 11 against Yushin Okami.

Palhares and his physician Michael Simoni revealed the information to Tatame.com, but neither specified which knee was injured.

Palhares has opted not to undergo surgery. But he won't rule out having surgery if advised to do so at a later date.

"In 15-20 days I will do another (MRI) to double-check my knee," Palhares told ESPN.com. "What doesn't kill you makes you stronger."

"It wasn't a simple injury, but I'm okay," Palhares said. "It's a new challenge for me, a new fight that I'll have to fight now.

"My focus has changed, but the determination is even bigger. I'll be back a better fighter."

Palhares (14-4) was looking to rebound from a first-round TKO loss to Alan Belcher on May 5. He entered that bout on a three-fight win streak.

The knee injury occurred during a sparring session.

"(He) got hurt while defending a takedown and won't be able to continue his trainings," Simoni said. "But, at first, there's no risk to need a surgery."

Palhares agreed to face Okami on short notice after Luiz Cane was forced to withdraw in June due to injury.

Okami (26-7) will now face Buddy Roberts at UFC 150 in Denver.