Bill Walker apparently left practice, and is getting an MRI on his right knee: (http://www.boston.com/sports/basketball/celtics/extras/celtics_blog/2009/09/walker_getting_1.html)Swingman Bill Walker left practice Wednesday and is headed for Boston to get an MRI on his surgically repaired right knee. Walker tore his left ACL while at Kansas State and then hurt the right knee in a workout with the Golden State Warriors in July 2008 and then had surgery a few weeks later.Hopefully, this is nothing but a precaution. I guess the silver-lining is that we're talking about a different knee, though it'd be nice to get through one day without mention of one.