It was informed by the world number three herself on Aug 19.
Informing about her decision, the Belgian tennis superstar said, "Two weeks of rehab was not enough to heal this injury. Obviously I'm very disappointed. I trained very hard this summer and felt in a good shape to play the US Open."
And added, "Now there is nothing else I can do than to rest and have treatment every day. If a gradual approach is not taken, I will relapse in the same injury, and therefore I have also no other possibility than to withdrawal from the tournaments in Tokyo and Beijing."
Clijsters, a three-time US Open champion, who also skipped Wimbledon this year with a foot injury, said she would have to skip tournaments in Japan and China scheduled for September and October. Just last week, she made clear about her aims to play in the London Olympics in 2012.
Clijsters found support from Maria Sharapova, who herself has missed quite a number of tournaments due to injuries. Sympathising with Clijsters, the Russian said, "It's probably one of the most frustrating feelings for an athlete just sitting there knowing that even before the tournament your name is not going to be in the draw."
And added, "It's tough, but I think, Kim, like many of us knows what it's like to deal with tough moments like this."