Spondylitis (involvement of vertebral bodies) | Typically located within bone marrow at one or more of the four corners of vertebral bodies. If located at the corners: spondylitis anterior ( = Romanus lesion) or spondylitis posterior |
Spondylodisciitis (involvement of intervertebral discs) | Located within bone marrow at cortical plate adjacent to intervertebral disc (Andersson lesion) |
Arthritis of zygoapophyseal joints (facet joint arthritis) | Any facet joint from C2 to S1 may be involved; usually associated with bone marrow oedema within spinal pedicles (posterior of spinal canal) |
Arthritis of costovertebral (CV) joints | Any CV joints from Th1 to Th12 may be involved; associated with bone marrow oedema near CV joint, extending to pedicles, posterior aspect of vertebral bodies (lateral of spinal canal) and neighbouring rib |
Enthesitis of spinal ligaments | Possibly affected entheses: supraspinal ligament, interspinal ligaments, ligamenta flava |
Syndesmophytes/ankylosis | Bridging (at the corners of the vertebral bodies) or fusion (new bone formation within the intervertebral disks) occurs in long-standing disease. |