First, there is the mechanical limitation that the bones don't move together properly- notice how the lower osteophyte (bone spur) formation might get in the way of a spine stretch or bend.
Second, also in this disc space of the spine are thousands of nerve fibers. If the discs are not in place to protect nerves, the are "crushed" by the bones. The herniation and bulging also place a stress on nervous tissue.
Facet joint arthritis makes lateral spinal movements (side bends/mermaids) more difficult.
Lumbar Stenosis causes a compression into the middle of the spinal column. This compresses nerves for lower back and limbs.
Arthritic conditions cause movement issues mechanically- Growth of bone (or loss of bone) on the moving, articulating facets can irritate nerves in the joint and will limit range of motion. This can occur anywhere there is a bone to bone connection. I've placed here mostly images of spinal bone connections, but this is also true for shoulders, knees, hips, wrists, ANY joint
Arthritis can be local due to specific injury- accidents etc. or from uneven pressures on the joints. Rheumatic arthritis- (See pic in prev post.) would be more systematic.
Stenosis is another way that nerves are compressed and irritated. I had always believed it to be more of a cartilage compression on the central nervous cord, but this image also makes it look like bone growth into the central canal may contribute.
Several of you have at least one of these conditions and have asked about them. Everyone has different genetics and different mechanical demands they have experienced in their different movement patterns. Any bone or cartilage that is changed or moved will translate to a change in movement. Know your limits- "Own" your limits (cheesy), but really... learn to be especially strong in areas where your body might be challenging you.- Don't be afraid to be strong in a modified position. This discussion is broad, but feel free to ask me about modifications specific to your situation.
ANY Movement is a great way to keep joints mobile and healthy- Use your core muscles to help alleviate mechanical stress on your spine. Use your leg muscles to alleviate stress on your hips and knees. Dance! Walk! Swim! Run!
Pilate!