Trail Blazers center Festus Ezeli had his left knee injected with a bone marrow aspirate concentrate and Orthovisc today in Chicago, the team announced.
The injection, performed by Dr. Brian Cole, is intended to alleviate pain and improve function.
Ezeli will be sidelined for six weeks.
The former Warriors big man signed a two-year, $15.1 million contract with Portland in July.
The second year is only partially guaranteed.
Ezeli missed the entire 2013-14 season after undergoing reconstructive surgery on his right knee.
He missed over two months last season because of arthroscopic surgery on his left knee.
Portland Trail Blazers media services contributed to this story