What does seronegative mean? The doctor tells me I have a sacroiliac joint problem that is seronegative.

Seronegative means blood tests came back negative for rheumatoid factor (RhF). RhF is positive when the joint problem is associated with some form of rheumatoid arthritis. Anyone who is seropositive likely has some type of underlying inflammatory cause of their pain.

When any part of the spine (including the sacrum and sacroiliac joints) is involved and there's an inflammatory cause, the condition is referred to as a spondyloarthropathy. The most common seropositive spondyloarthropathies affecting the sacroiliac joint include ankylosing spondylitis, reactive arthritis (also categorized as Reiter's syndrome), enteropathic arthritis associated with inflammatory bowel disease (IBD), and psoriatic arthritis.

If you are seronegative, it's likely you don't have any of these problems causing your symptoms. Another test that can be used to make sure the sacroiliac joint is even the cause of the problem is a steroid injection directly into the joint. Pain relief is an indication that the sacroiliac joint was, indeed, the source of the problem(s).