Foot dysfunction can play a significant role in either the causation or contribution to back pain. A loss of stability around the spine can lead to increased stress on the spinal components (discs, bones, joints or ligamets). Dysfunctional foot mechanics can vary from being a foot which is too mobile, thereby allowing excessive movement to occur (usually resulting in muscle spasms); to rigidity which does not allow for enough load attenuation and thus jarring of the joints. 

A difference in leg length can also play a role. Although this is common, the body’s ability to compensate for it decreases with age and may therefore influence the onset of back pain.

The other area to consider is asymmetry in gait. If one was to have differing speeds of walking between left and right leg it could be compared to a misaligned car. If you let the steering wheel go; you veer off in one direction. The body has to compensate for this and this compensation may be pathological (cause injury).