Facet Arthropathy¶
Definition¶
Facet arthropathy (facet joint osteoarthritis) is the degenerative deterioration of the facet (zygapophyseal) joints, characterized by cartilage loss, joint space narrowing, subchondral sclerosis, osteophyte formation, and joint effusion. It is a major contributor of back/neck pain and spinal stenosis.
Pathophysiology¶
- Disc degeneration and height loss increase loading on the facet joints
- Progressive cartilage erosion leads to bone-on-bone contact
- Osteophyte formation and capsular hypertrophy narrow the lateral recess and foramen
- Synovial cysts may develop from the degenerated joint
Imaging Findings¶
CT — Best for Bony Detail¶
- Joint space narrowing
- Subchondral sclerosis and cysts
- Osteophyte formation from articular processes
- Vacuum phenomenon within the facet joint
- Facet hypertrophy narrowing the lateral recess or foramen
MRI¶
| Finding | Appearance |
|---|---|
| Joint effusion | T2-bright fluid within the facet joint (>1 mm) |
| Cartilage loss | Narrowed joint space |
| Periarticular edema | T2/STIR hyperintensity around the joint (active inflammation) |
| Synovial cyst | T2-bright, well-defined cyst arising from the joint; may have low-signal rim |
| Facet hypertrophy | Enlarged articular processes encroaching on lateral recess or foramen |
Grading (Pathria Classification)¶
| Grade | Description |
|---|---|
| 0 | Normal |
| 1 | Mild — joint space narrowing, small osteophytes |
| 2 | Moderate — sclerosis, moderate osteophytes, moderate narrowing |
| 3 | Severe — marked osteophytes, severe narrowing, subchondral cysts |
Clinical Pearl
Facet arthropathy is a common cause of axial (non-radicular) low back pain, but diagnosing it as the pain source is challenging because facet degeneration is nearly universal with aging and is often asymptomatic. Facet joint effusion on MRI and bone marrow edema adjacent to the facet on STIR are the best imaging markers for an actively symptomatic facet joint. These findings can help target diagnostic medial branch blocks, which, if positive, can lead to radiofrequency ablation for longer-lasting pain relief.
Key Points¶
- Facet arthropathy is facet joint osteoarthritis — cartilage loss, sclerosis, osteophytes, effusion
- A major contributor to lateral recess and foraminal stenosis
- CT is best for bony changes; MRI for effusion, edema, and synovial cysts
- Facet effusion and periarticular edema on MRI suggest active/symptomatic disease
- Diagnosis of facet-mediated pain requires clinical correlation and often diagnostic blocks
- Synovial cysts from degenerated facets can cause radiculopathy
References¶
- Pathria M, Sartoris DJ, Resnick D. Osteoarthritis of the facet joints: accuracy of oblique radiographic assessment. Radiology. 1987;164(1):227-230. doi:10.1148/radiology.164.1.3588910. https://pubmed.ncbi.nlm.nih.gov/3588910/
- Weishaupt D, Zanetti M, Boos N, Hodler J. MR imaging and CT in osteoarthritis of the lumbar facet joints. Skeletal Radiology. 1999;28(4):215-219. https://pubmed.ncbi.nlm.nih.gov/10384992/
- Pathria grading system of lumbar facet joint degeneration. Radiopaedia.org. https://radiopaedia.org/articles/pathria-grading-system-of-lumbar-facet-joint-degeneration
- Weishaupt grading system of lumbar facet joint degeneration. Radiopaedia.org. https://radiopaedia.org/articles/weishaupt-grading-system-of-lumbar-facet-joint-degeneration
- Lattig F, Fekete TF, Grob D, Kleinstück FS, Jeszenszky D, Mannion AF. Lumbar facet joint effusion in MRI: a sign of instability in degenerative spondylolisthesis? European Spine Journal. 2012;21(2):276-281. https://pmc.ncbi.nlm.nih.gov/articles/PMC3265597/
- Acosta Julbe JI, Gottreich JR, Ermann J, et al. Reporting of facet joint inflammation in lumbar spine MRI studies in patients with low back pain. Spine (Phila Pa 1976). 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11042993/
- Zhou X, Liu Y, Zhou S, et al. The correlation between radiographic and pathologic grading of lumbar facet joint degeneration. BMC Medical Imaging. 2016;16:27. https://pmc.ncbi.nlm.nih.gov/articles/PMC4812623/