The spine problems that cause leg pain only aren’t that much different from those that cause back symptoms. What differs is how we treat the different problems.
Generally speaking, the vast majority of spine problems are due to degenerative changes that are a natural part of aging. Not everyone has the same degree of degenerative change nor does everyone have the same amount of pain from the same degree of degeneration. Some folks have a lot of pain with minimal change while others have extensive changes but have very little pain. That is what makes this specialty challenging for us spine specialists.