Supination of the feet can lead to Achilles tendinitis, iliotibial (IT) band syndrome and plantar fasciitis, because of the extra stress the foot absorbs. Supination happens when the foot does not roll inward far enough after landing, according to About.com.
People suffering from IT band syndrome, plantar fasciitis or Achilles tendinitis should look at their shoes to see if supination is the underlying cause. If a shoe wears all along the outside edge, stretching the side too much, supination is the likely culprit. Putting a shoe down on a flat surface makes the shoe tilt outward. People with tight Achilles tendons and high arches are most likely to supinate their feet. People who are not certain should visit a technical running shoe store in their area -- one that targets serious walkers and runners. Most stores offer free gait analysis as they try to find the right shoe for each customer. Some walking and running shoes correct supination, notes About.com.
Several remedies exist for supination. One is a pair of shoes with curved lasts to permit shoes to pronate, or roll inward on landing. Putting on a pair of lightweight trainers allows more freedom of motion for feet. Stretching hamstrings, quads, calves and the IT band also cuts down on supination, as stated by About.com.