Nike Co-Founder Knight Steps Down as CEO  SAN FRANCISCO (Reuters) - Nike Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=NKE.N target=/stocks/quickinfo/fullquote"&gt;NKE.N&lt;/A&gt; co-founder  Philip Knight, who helped transform a small start-up into the  world's biggest athletic shoe company, will step down as chief  executive officer, the company said on Thursday.