Source: University of California, Berkeley
Orthoses, popularly called orthotics, are foot supports made of various materials (foam, leather, plastic, fiberglass, graphite) that fit inside shoes. Some are flat, some molded; some have gel fillings. By cushioning and helping support the foot, they can help reduce problems associated with bunions, plantar fasciitis, and some other foot conditions. They can also make foot motion more efficient and correct structural imbalances that cause pain in the knees and hips, and they are good shock absorbers when you exercise.