As a foot and ankle specialist, I am probably not the best person to answer your question. But, there are some lower extremity conditions which contribute to low back pain. Two common problems causing back pain are limb length discrepancy and
overpronation. Limb length discrepancy, where one leg is longer than the other, results in compensation at the foot and ankle, but also alters the gait and affects the lower back.
Overpronation, especially when one foot overpronates more than another foot, can alter gait, resulting in low back pain. Any foot or ankle problem which alters the way you walk can cause low back problems. These two are problems which may be associated with low back pain, but are not necessary associated with foot and ankle pain.