I had a lumbar fusion at the l5 s1 level five years ago . i am having lower back now. is the next level herniated or degenerative ?

Degenerative : Unfortunately one of the late complication of spinal fusion is adjacent disc disease. Since your fusion was the lowest mobile level all the stress has been shifted to the l4-5 level. Most symptoms arise from degenerative changes in the disc and the facets, but herniation may also occur. A MRI would beneficial. See your spinal surgeon.

Very possible: Adjacent level degenerations 15% at 15 years see your surgeon for evaluation very few people with a fusion done with a back inscion have a completely pain free back at all activity levels in all positions for all times you can still get old around your fusion.

Hard to say: Certainly one cause can be the development of adjacent level disease, and it is probably the most common cause. There are also other structures in the area that can cause pain such as the sacroiliac joints and the facet joint, hips, etc. Thank you for your question. A detailed history, exam and studies can usually determine the cause.