The natural inward roll of your foot while running is called pronation, and most runners fall into one of three main categories: over-pronator, neutral or supinator. The supinator's foot tends to roll outward, placing stress on the outer edges of the foot. Supinators require cushioning, and the best trail shoes will provide extra cushioning to help keep the foot injury-free during movement.
Supinators, who are also called under-pronators, tend to roll toward the outside edge of their feet, which decreases the ability to control the foot when landing. If the wear on your running shoes is greater on the outside edge than any other part, you may be a supinator. This outside rolling can pull the hips and pelvis out of alignment and can lead to conditions like Illiotibial band syndrome, plantar fasciitis and Achilles tendonitis.
Since supinators land with greater impact, trail shoes that provide maximum cushioning are the best. Trail shoes are essentially running shoes with soles made for off-road activity; these outsoles are enhanced for greater traction on surfaces like rocks, mud, grass and roots. The ideal trail running shoes will also provide plenty of arch support, stability and adequate room in the toe box. Comfort and ease of movement are also necessary qualities.