The Science of Spinal Stenosis
Spinal stenosis involves narrowing of the spaces within your spinal canal, creating compression of neural structures. This narrowing can occur in the central canal (central stenosis) where the spinal cord or cauda equina travels, or in the lateral recesses and foramina where individual nerve roots exit. The narrowing typically develops gradually through multiple mechanisms. Degenerative changes in the discs can cause bulging into the spinal canal, while arthritis of the facet joints leads to bone spur formation and joint enlargement. The ligamentum flavum, which runs along the back of the spinal canal, can thicken and buckle inward, further reducing available space. As these structures encroach on the neural space, they create a mismatch between the space available and the space needed for optimal neural function. The compression may be positional - worsening when your spine is extended and improving with flexion, which explains why many people find relief when leaning forward or sitting.
Contributing Factors
Your spine's position significantly affects the amount of space available within the spinal canal. When you extend your back or stand upright, the canal diameter decreases due to buckling of the ligamentum flavum and narrowing of the lateral recesses. This positioning can worsen compression of already compromised neural structures.
Flexing your spine has the opposite effect - it increases canal dimensions by stretching the ligamentum flavum and opening up the lateral recesses. This is why many people with spinal stenosis naturally adopt a slightly flexed posture when walking or find relief when leaning on a shopping cart.
Walking on an incline often feels easier than walking on flat ground because the incline naturally puts you in a slightly flexed position. Similarly, cycling is usually tolerated better than walking because the cycling position maintains spinal flexion while allowing cardiovascular exercise.