George Washington won its 15th straight game last night, but the bigger news is that star forward Pops Mensah-Bonsu twisted his knee just before halftime and didn’t return. Mensah-Bonsu, the team’s second-leading scorer and rebounder, will be evaluated today. We (or, more likely, some alert DCist reader) will have an update on his status when it becomes available. Reserve forward Regis Koundjia stepped up in Mensah-Bonsu’s absence, chipping in with 13 points, 5 rebounds and…