Can you spot the problem?

Take a look at the pictures before proceeding, knowing that this gal presented with L sided outside knee pain and see if you can tell what may be wrong. She does wear orthotics. 

Take a good look at the lateral flare on each of these shoes. Yes, it is a Brooks Pure series with a 4mm drop. Yes the shoe has a medial (sl larger) and lateral flare, posteriorly and anteriorly.

Do you see the discoloration and increased wear on the lateral heel counter on the left compared to the left? There is also increased wear of the lugs on the outside of this left shoe. The forefoot is also worn into slight varus, but this difficult to see. The shoe, especially in combination with her orthotic, is keeping her in varus (ie inverted) for too long, taking her knee outside the saggital plane and contributing to her knee pain.