Wall reported discomfort in his knee and examinations Thursday came up with a diagnosis of the early stages of a non-traumatic stress injury.
Wizards officials said Wall will miss eight weeks -- all of training camp and about the first month of the regular season. Washington opens the season Oct. 30 at Cleveland.
"We're all disappointed for John after how hard he worked this summer and how excited he was to begin training camp but we feel fortunate that we caught the injury early and that he will be able to return with the vast majority of the season still in front of us," said Wizards President Ernie Grunfeld.
Wall was the first overall selection in the 2010 draft. He averaged 16.3 points, 8 assists and 4.5 rebounds in 66 games last season.
"My teammates and I are all excited to build on the improvement we made at the end of last season, and I know they will continue to make great progress while I get through this setback," Wall said. "I will work extremely hard to make sure I get back as soon as possible so I can re-join them and help our team continue to improve."