hi sir/madam, Thanks for your question on Healthcare Magic. Possible causes are- 1. Poor Hip Mobility:- With every step we take our hip and pelvis move in three planes of motion. If we have any lack of motion in our hip it will cause the spine to move more than it is designed to move. Overtime this increased motion can begin to create inflammation and compression of the nerves that exit the spine. This leads to sciatica and lower back pain. 2. Limited Foot and Ankle Mobility:- Every time our foot hits the ground when we are walking studies demonstrate that the body needs to absorb 2-3 times our body weight in forces. Those forces end up traveling up into the spine. If the foot is stiff and does not flatten when we walk like it is designed to do it will cause an increase in forces transmitted into the spine. The increased forces cause increased compression and can irritate the joints and nerves in the spine. 3. Decreased Hip Strength:- It is very common to see people walking with a slight lead to one side when the foot lands on the ground. This is an indicator that the lateral part of the hip is weak (glute medius). When this happens, the body compensates by leaning to that side. When the body leans to that side is causes compression of the nerves on the same side of the spine. 4. Stiff Upper Back:- With every step we take we also have an arm swing in the opposite direction. This arm swing causes our upper back to rotate. If we have limited upper back rotation it will cause increase rotation in the lower back. This increased rotation can lead to increased compression and irritation to the joints and nerves in the spine. 5. Stenosis or Arthritis in the spine:- Research indicates that if you are over 55 years old, have pain in your lower back with walking or standing and it goes away when you sit, there is a 97% chance you have arthritis in your spine. This arthritis predisposes you to have pain with walking in your spine. If you fix all of the things we have mentioned earlier then you can walk without pain even when you have stenosis or arthritis in the spine. Don’t let it be an excuse. Just know it is one of the 5 reasons why your back may hurt when you walk. Hope it was helpful. Stay healthy,Stay safe.