As runners, we know our first line of defense against overuse injuries is good-quality, low-mileage running shoes. It is our job not only to buy the right pair but also, to replace them regularly. When injuries occur you need to review your training to be sure you didn't put too many miles on your body or your shoes. But there's a third factor - shoe defects.
Even if we know our feet and biomechanics and buy the right shoe for the job, manufacturer defects can undermine the best training and injury prevention strategies. A healthy runner without previous injuries, running similar distances and speed who suddenly experiences pain or injury after buying a new pair of shoes should consider the possibility of a defect.
The main purpose behind a running shoe is to hold your foot stable and to provide shock absorption. Defective running shoes that don't hold your feet in a neutral position may accentuate preexisting biomechanical problems like excessive pronation or supination. And when they may not provide proper shock absorption, or worse, they may have uneven shock protection, it can throw your gait into injury-prone asymmetry. This can lead to aches, pains or time off for an injury.
Check the shoes right out of the box. Put them on a flat surface and hold the top of the shoe while rocking it in and out. The shoes should remain even and shouldn't roll. If they are new and roll, they won't provide motion control while running. The small stitched rectangular area in the back of the shoe (heel counter) should be straight and sturdy when you hold both shoes at eye level. Also, the upper should be positioned straight and glued securely into the sole. Eyelets should be even. Air pockets and gel pockets must be properly inflated. If collapsed on one side, the result can be devastating injury and pain. Check your shoes regularly for excessive wear throughout their entire "life." Arch supports can lose their resiliency. Retire your shoes after 300-500 miles.