Jamison will be re-evaluated next week, after the swelling goes down.
He had an MRI exam Thursday, a day after getting hurt while trying to block a shot by Zydrunas Ilgauskas in Washington's 109-104 preseason victory over the Cleveland Cavaliers.
The Wizards have preseason games left against Atlanta, Philadelphia and Chicago. They open the regular season Oct. 27 at Dallas.
Jamison is a two-time All-Star who led the Wizards in scoring average last season at 22.2 points. Washington lost starters Gilbert Arenas, Brendan Haywood and DeShawn Stevenson to injuries for long stretches and finished 19-63.