The 21-year-old has not played for the club since starting in a 4-0 Eredivisie win over Heerenveen on March 8.
And Lewis will play no part in the UEFA Europa League play-off matches against Heerenveen - or the final if his side progress - after a brief statement on the club's official website confirmed he underwent surgery on Friday.
"On Friday in Orthopedium Clinic in Delft, Fernando Lewis underwent successful surgery on his right knee," it read.
"During the operation, the meniscus of the outer joint was treated.
"It is expected that the 21-year-old attacker can re-join the group at the start of the new season."
Lewis has made nine appearances in all competitions for AZ this season, scoring twice.
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