If you have a narrow foot then you need to pay attention to the outsole width. A narrow foot typically needs a narrower outsole then a wide foot. Here are two medium shoe outsoles which illustrate the difference.
This person has a narrow foot and the shoe on the right was too wide (even though it’s a medium width) creating side to side motion in the shoe, resulting in plantar fasciitis and achilles tendonitis. Both of these conditions were non-existent in the narrower (also medium) shoe, pictured above on the left side.
Having a shoe that it too wide can be just as bad as a shoe that’s too narrow. Best to match the width of your foot to the width of the shoe.
Dr. Jenny Sanders Shoe Blog 