Synovial Swelling

DIFFERENTIAL DIAGNOSIS

Common

• Osteoarthritis
• Inflammatory Arthropathy
• Tophi of Gout or Pseudogout

Less Common

• Pigmented Villonodular Synovitis
• Focal Nodular Synovitis
• Synovial Osteochondromatosis
• Septic Arthritis
• Lipoma Arborescens
• Amyloid
• Synovial Hemangioma
• Synovial Sarcoma
• Synovial Chondrosarcoma

Rare but Important

• Lymphoma

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

• Diagnosis of synovial mass is based on several features in addition to US characteristics

Clinical features

– Age of patient, disease onset, & clinical course

Pattern of disease

– Which joint or joints are affected & which part of these joints are affected

Radiographic features

– Joint space narrowing, osteophytes, erosions, mineralization, juxtaarticular osteopenia

US characteristics

– Intraarticular or extraarticular mass

– Degree of synovial thickening

– Localized or diffuse synovial thickening

– Degree & character of joint effusion

– Joint space narrowing, osteophytes, erosions, mineralization

– Degree of synovial hyperemia

– Degree of periarticular inflammation

Serology: Inflammatory markers, antinuclear factor, rheumatoid factor; antibodies to mutated citrullinated vimentin; antibodies to cyclic citrullinated peptide

Histology

– US-guided biopsy for histology very useful to differentiate many types of synovial overgrowth

– Cannot distinguish between synovial inflammation secondary to osteoarthritis, inflammatory arthropathy, or nontuberculous infective arthropathy

Helpful Clues for Common Diagnoses

• Osteoarthritis

Knees, hips, hands, & feet

Increasing age, trauma, excessive physical use, genetics, & obesity are all predisposing factors

Variable synovial inflammation is more common in osteoarthritis than previously thought

Tends to occur close to areas of pathologically damaged bone & cartilage

Only modest correlation between severity of osteoarthritis & degree of synovitis

– Generally easier to quantify degree of periarticular inflammation on MR than US
• Inflammatory Arthropathy

Synovial proliferation with inflammatory arthropathy

– Diffuse echogenic or hypoechoic synovial proliferation

Osteoarthritis changes (marginal osteophytosis, localized joint space narrowing, meniscal degeneration, articular debris) less pronounced

Mild to moderate synovial hyperemia typical
• Tophi of Gout or Pseudogout

Particularly joints of hands, feet, & knee

– Gout → urate crystal deposition

– Pseudogout → calcium pyrophosphate dihydrate deposition

Tophi are more common in gout

Periarticular location

– Soft or hard tophi

– ± synovial or intrameniscal deposition

Hyperechoic aggregates in synovial fluid

– Urate sand or snowstorm appearance

Gout: Thin echogenic band on surface of cartilage (“urate icing”)

Pseudogout: Thin echogenic band in midzone of articular cartilage

Helpful Clues for Less Common Diagnoses

• Pigmented Villonodular Synovitis (PVNS)

Now known as giant cell tumor of tendon sheath

Benign proliferative synovial disorder

– Affects synovium of joint, bursa, or tendon sheath

Knee > hip > ankle > shoulder

Joint involvement is diffuse though may predominate in 1 or several areas of joint

Usually moderate to high degree of hyperemia

– May show little or no hyperemia

Characteristic MR pattern on gradient echo imaging due to paramagnetic effect of hemosiderin

– Foci of synovial hypointensity due to hemosiderin

– Hemosiderin is present in 85% of pigmented villonodular synovitis (PVNS) cases (i.e., lack of hemosiderin does not exclude diagnosis)
• Focal Nodular Synovitis

Localized to single area of synovium

– Although histologically identical, focal disease behaves differently from diffuse disease

– PVNS & focal nodular synovitis (FNS) now considered different entities

– FNS contains less hemosiderin, does not have frond-like projections & becomes more pedunculated rather than more extensive with growth
• Synovial Osteochondromatosis

Proliferation & metaplastic transformation of synovium

Affects any synovium, including synovium-lined joint, bursa, or tendon

– Knee > elbow > hip > shoulder

Active synovial proliferation & cartilaginous metaplasia → inactive phase

– Intrasynovial cartilage nodules detach to lie free in joint & ossify

– Nodules may consist of cartilage, cartilage/bone mixture, or mature bone with marrow fat

Mineralized nodules are hyperechoic; cartilage nodules are hypoechoic

Variable-sized joint effusion

± erosion of adjacent cartilage & bone

– Especially in less distensible joints (hip)

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Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

DIFFERENTIAL DIAGNOSIS

Common

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

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Synovial Swelling

Synovial Swelling

Less Common

Rare but Important

Helpful Clues for Common Diagnoses

Helpful Clues for Less Common Diagnoses

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Synovial Swelling

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