The 22-year-old had just over two-and-a-half ounces drained by the team's physician early on Monday, according to a Lakers spokesman.
Bynum, who has averaged 9.1 points and 7.7 rebounds in the post-season, hyperextended his right knee a month ago against the Oklahoma City Thunder.
Although the seven-foot center has continued to start for the defending NBA champions, the injury has limited his effectiveness and playing time.
"He's not a hundred percent but he's throwing himself in there. He'll do the job."
The Lakers will face arch-rivals the Boston Celtics in the best-of-seven NBA Finals with Game One being played in Los Angeles on Thursday.
(Writing by Mark Lamport-Stokes; Editing by Frank Pingue)