The cause of having one foot larger than the other typically relates to limb length discrepancy. Many people have one leg that is longer than the other, which corresponds with one larger foot, according to state-registered chiropodist Philip Mann for Footpodiatrist.com.
With limb length discrepancy, the longer leg pushes down more on the corresponding foot, which causes the arch to lower, thus elongating the foot, explains Mann. People with limb length discrepancy often have scoliosis in the back, which tilts the hip and forces one leg to be longer in length. Limb length discrepancy may not cause pain in some people; however, others may experience knee problems, heel pain, tendonitis and metatarsalgia, or suffer from corns and calluses.
Foot care is a key concern for people with one foot larger than the other. When selecting shoes, choose a shoe size that fits the larger foot, recommends the National Institute on Aging. Shoe sizes and the length of feet may also change as a person ages, so it may be helpful to have feet measured before purchasing any shoes. Feet are largest at the end of the day, which is often the ideal time to measure for a proper shoe fit.