<aside>
Synovial hypertrophy refers to an abnormal thickening of the synovial membrane lining joints, tendon sheaths, or bursae. It typically results from chronic inflammation, synovial proliferation, or reactive changes, and is a key feature in many inflammatory arthritides.
</aside>
| Trigger | Effect |
|---|---|
| Chronic inflammation (e.g., RA) | Proliferation of synoviocytes and infiltration by immune cells |
| Increased vascularity | Synovium becomes hyperemic and edematous |
| Fibrosis or pannus formation | Can erode cartilage and bone |
Etiologies:
| Inflammatory | Non-inflammatory / Mechanical |
|---|---|
| Rheumatoid arthritis (RA) | Osteoarthritis (secondary mild synovitis) |
| Psoriatic arthritis | Meniscal tear with parameniscal cyst |
| Juvenile idiopathic arthritis (JIA) | Synovial chondromatosis |
| Crystal arthropathy (e.g., gout) | PVNS (pigmented villonodular synovitis) |
| Systemic lupus erythematosus (SLE) | Trauma-induced hemarthrosis or effusion |
| Symptoms | Signs |
|---|---|
| Joint pain, stiffness | Swelling, particularly periarticular |
| Morning stiffness (>30 minutes) | Warmth, joint tenderness |
| Restricted motion | Crepitus (less common in early stages) |
| Modality | Imaging features |
|---|---|
| US | Modality of Choice for Dynamic and Early Detection |
| • Hypoechoic, non-compressible synovial thickening | |
| • Hyperemia on Doppler: Suggests active synovitis (inflammatory activity) | |
| • Joint effusion: Anechoic or hypoechoic fluid, often coexisting | |
| • Erosions at margins: Chronic inflammatory damage (especially in RA) | |
| MR | • T2/STIR hyperintense synovium with post-contrast T1 enhancement: Confirms vascularized hypertrophic synovium |
| • Chronic inflammatory arthritides: Bone marrow edema, cartilage loss, erosions |
Key conditions with synovial hypertrophy:
| Condition | Unique Features |
|---|---|
| Rheumatoid arthritis | Bilateral, symmetric, erosive changes, pannus |
| Psoriatic arthritis | Asymmetric, "ray pattern", DIP involvement |
| PVNS (Pigmented Villonodular Synovitis) | Localized or diffuse synovial overgrowth, blooming on GRE |
| JIA (Juvenile idiopathic arthritis) | Knee and wrist involvement common, may show effusion + thickening |
| Synovial chondromatosis | Intra-articular cartilaginous nodules with or without calcification |
Grading of Synovial Hypertrophy (EULAR/OMERACT Guidelines)
| Grade | Description |
|---|---|
| 0 | No synovial thickening |
| 1 | Mild thickening; bulge without extension beyond joint line |
| 2 | Moderate thickening; extending beyond joint line |
| 3 | Severe thickening; large bulging of hypertrophic synovium |
Effusion vs Hypertrophy on US