Objectives: The facet joints (FJ) can be a potentially important source of symptoms because of the high level of mobility and load forces, especially in the lumbar area. We reviewed the anatomy, biomechanics, and possible sources of pain of the FJ, natural history, and risk factors of lumbar FJ osteoarthritis and briefly reviewed the relevant imaging methods.
Methods: PubMed and MEDLINE databases (1950-2006) were searched for the key words "facet joints," "zygapophyseal joints," "osteoarthritis," "low back pain," and "spondyloarthritis." All relevant articles in English were reviewed. Pertinent secondary references were also retrieved.
Results: The FJ play an important role in load transmission; they provide a posterior load-bearing helper, stabilizing the motion segment in flexion and extension and also restricting axial rotation. The capsule of the FJ, subchondral bone, and synovium are richly innervated and can be a potential source of the low back pain. Degenerative changes in the FJ comprise cartilage degradation that leads to the formation of focal and then diffuse erosions with joint space narrowing, and sclerosis of the subchondral bone. Because the most prominent changes occur in bone, the best method of evaluation of the FJ is computed tomography. Risk factors for lumbar FJ osteoarthritis include advanced age, relatively more sagittal orientation of the FJ, and a background of intervertebral disk degeneration.
Conclusions: An up-to-date knowledge of this subject can be helpful in the development of diagnostic techniques and in the prevention of lumbar FJ osteoarthritis and low back pain and can assist in the determination of future research goals.