The 21-year-old tennis player withdrew from the WTA Rogers Cup in Montreal in late July because of a shoulder injury after a marathon second-round win over Marta Domachowska of Poland.
A scan revealed two small tears in her right shoulder. She later said: "It hurts me so much to miss the Olympics and the U.S. Open. I think this will be the first grand slam I have ever missed."
"I had been playing with the pain for a rather long time," Sharapova said on her Russian-language website. "Even in everyday life, during sleep, I felt it [the pain]."
The Russian tennis star is currently doing extensive rehab and strength work in Arizona. The treatment is due to last several months.
"I knew that this was more than just inflammation. It's a pity that the doctors failed to make the correct diagnosis," Sharapova said, adding that the right diagnosis would have shortened the recovery time.
Sharapova is now No. 5 in the Women's Tennis Association world rankings, just below Russia's Elena Dementieva who won an Olympic gold medal in the final of the women's singles in Beijing.
