1 Facet Arthropathy: An Arthritic Back Facet arthropathy (FA) is a form of degenerative arthritis that affects the spine. 2  It targets the facet joints of the spine and causes arthritis-like pain in the back. 3  Facet 4  …. Lumbar Facet Arthropathy: Treating Lower Back Pain Lower back pain is a common problem in the modern world.