Arthritis is the degeneration of any joint in the body. The lower back is the most common site of arthritis back pain, because it bears more of the body's weight. In the spine, arthritis can result from disc degeneration and loss of water content. When that happens, the protective joint cartilage wears away and the facet joints begin to degenerate and develop arthritis. Symptoms include back pain, numbness, tingling, and weakness that may radiate to the buttocks or legs.