| M45 | Ankylosing spondylitis | NON-BILLABLE CODE |
| M45.0 | Ankylosing spondylitis of multiple sites in spine | BILLABLE CODE |
| M45.2 | Ankylosing spondylitis of cervical region | BILLABLE CODE |
| M45.3 | Ankylosing spondylitis of cervicothoracic region | BILLABLE CODE |
| M45.4 | Ankylosing spondylitis of thoracic region | BILLABLE CODE |
| M45.5 | Ankylosing spondylitis of thoracolumbar region | BILLABLE CODE |
| M45.6 | Ankylosing spondylitis lumbar region | BILLABLE CODE |
| M45.7 | Ankylosing spondylitis of lumbosacral region | BILLABLE CODE |
| M45.8 | Ankylosing spondylitis sacral and sacrococcygeal region | BILLABLE CODE |
| M45.9 | Ankylosing spondylitis of unspecified sites in spine | BILLABLE CODE |
| M45.A | Non-radiographic axial spondyloarthritis | NON-BILLABLE CODE |
| M45.A0 | Non-radiographic axial spondyloarthritis of unspecified sites in spine | BILLABLE CODE |
| M45.A1 | Non-radiographic axial spondyloarthritis of occipito-atlanto-axial region | BILLABLE CODE |
| M45.A2 | Non-radiographic axial spondyloarthritis of cervical region | BILLABLE CODE |
| M45.A3 | Non-radiographic axial spondyloarthritis of cervicothoracic region | BILLABLE CODE |
| M45.A4 | Non-radiographic axial spondyloarthritis of thoracic region | BILLABLE CODE |
| M45.A5 | Non-radiographic axial spondyloarthritis of thoracolumbar region | BILLABLE CODE |
| M45.A6 | Non-radiographic axial spondyloarthritis of lumbar region | BILLABLE CODE |
| M45.A7 | Non-radiographic axial spondyloarthritis of lumbosacral region | BILLABLE CODE |
| M45.A8 | Non-radiographic axial spondyloarthritis of sacral and sacrococcygeal region | BILLABLE CODE |
| M45.AB | Non-radiographic axial spondyloarthritis of multiple sites in spine | BILLABLE CODE |
