( CNN ) -- Olympic gymnast Shawn Johnson , who announced over the weekend she would retire because of recurring knee problems , said Monday the decision was one of the hardest of her life and that she thinks its impact has n't truly hit her . `` Having that period of my life over with is surreal . I do n't think it 's settled in yet . It just came to a point where my body could n't take anymore and kept telling me I had to face the science , '' she told CNN 's Erin Burnett . `` It was definitely one of the hardest decisions I 've ever made , '' she said . Johnson , 20 , won one gold and three silver medals during the 2008 Olympics in Beijing . She also won a season of `` Dancing with the Stars , '' waltzing her way into the hearts of millions of American fans . Even though she wo n't be able to compete at the Olympics this year , Johnson told Burnett she still plans to go to London to cheer on her teammates . `` If I ca n't be on the podium competing , I 'll be in the stands cheering my head off for them , '' she said . Asked by Burnett what she plans to do next , Johnson said she will take a year off and then hopefully start college . `` I 've had that on my list ever since I was little and my parents are going to make sure that happens , '' said Johnson . `` As for career , I have no idea . I do n't even know what I 'm going to be doing tomorrow right now because my plans have changed a little bit , but I 'm excited to see what opportunities are going to arise . ''
Shawn has won two Olympic medals and a season of ` ` Dancing with the Stars '' She is retiring at 15 because of recurring back problems . ` ` It was definitely one of the hardest decisions I ' ve ever made , '' she said .