http://revach.net/article.php?id=1542

Section: Halacha   Category: Tshuvos
Rav Chaim Kanievsky - Freedom Of Movement

If someone completed Shmoneh Esrei but can't take three steps back because there is somebody behind him who is still in middle of Shmoneh Esrei, may he separate his feet or must he continue to keep them together?  Rav Chaim Kanievsky rules that there is no need for him to continue to keep his feet together and he even may move them to the side or lift his feet in the air if he so chooses. 

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.