Osteoarthritis of the spine: the facet joints
Facet joints (zygapophyseal joints) articulate the posterior vertebral column. Like other ageing synovial joints, they can be affected by osteoarthritis (FJOA), not only involving cartilage loss, but also compromising subchondral bone, synovium, capsule, ligaments and periarticular muscles. The associated imaging signs (joint space irregularity/narrowing, bone erosion, osteophytes and bone marrow or periarticular oedema) are most frequent at L4-L5 and L5-S1, and from C3 to C5 in the cervical spine.
Biomechanically, the facet joints and intervertebral disc are interdependent; facet joints normally bear 33% of axial load in extension. This load can increase to 70% when disc degeneration and FJOA are associated. Furthermore, dysfunction of the paravertebral muscles, which contribute to proprioception and motor control of spinal segments, have also been linked to
FJOA.Facet joints, being very well innervated by the posterior ramus of spinal nerves, may refer pain in specific but highly variable patterns. Although no clinical test or cluster of tests can accurately diagnose FJOA, controlled diagnostic anaesthetic blocks currently tend to represent the best diagnostic tool to confirm pain arising from the facet joints. > From: Gellhorn et al., Nat Rev Rheumatol 9 (2013) 216–224. All rights reserved to Macmillan Publishers Ltd.
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