Joint Effusion

DIFFERENTIAL DIAGNOSIS

Common

• Osteoarthritis

Less Common

• Inflammatory Arthropathy
• Crystal Arthropathy
• Infective Arthritis
• Hemarthrosis
• Lipohemarthrosis
• Pigmented Villonodular Synovitis
• Synovial Osteochondromatosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

• Characterization of underlying arthropathy relies on disease pattern rather than single US characteristic

Speed of onset, joints affected, severity of disease, age of patient, associated features, and radiographic and US appearances

Oligoarticular or polyarticular location is feature of both inflammatory or degenerative arthropathy
• US is helpful in assessing disease activity and characterization
• Amount and echogenicity of fluid are useful to note but lack specificity

Amount and appearance of joint fluid in osteoarthritis (OA), inflammatory arthropathy, repeated hemarthrosis, and septic arthritis may appear very similar

– Distinguish among these entities by noting concurrent US features, history, and clinical presentation

– Check especially for crystal aggregates, which are indicative of crystal arthropathy

– Crystal arthropathy can coexist with OA, infective arthritis, and other causes of joint effusion
• If joint fluid is hyperechoic, keep joint still for several minutes

Facilitates sedimentation of contents, which may help diagnosis

– If 2 layered, more likely hemorrhagic; infective fluid does not sediment readily

– If 3 layered, diagnostic of lipohemarthrosis

US-guided fluid aspiration is often necessary and very helpful

– Specimen for crystals needs to be sent fresh since saline or alcohol will dissolve crystals

Helpful Clues for Common Diagnoses

• Osteoarthritis

Most commonly affects knee, hip, interphalangeal, 1st carpometacarpal, triscaphe, wrist, acromioclavicular, and tarsal joints

Joint space narrowing, marginal osteophytosis, capsular swelling, synovitis, and effusion are US signs of OA

Variable increase in joint fluid

Variable degree of reactive-type inflammatory synovial proliferation

± variable periarticular inflammation

– Inflammatory component is important to note because this determines response to antiinflammatory medication

US is increasingly used to determine inflammatory component of OA and differentiate OA from crystal deposition disease or inflammatory arthropathy

Inflammatory element of OA is characterized by

– Capsular thickening, joint effusion, synovial proliferation, synovial and pericapsular hyperemia, edema of periarticular soft tissues

Helpful Clues for Less Common Diagnoses

• Inflammatory Arthropathy

Affects any synovial-lined joint

– Often bilateral and symmetrical

Ranges from single (monoarthropathy) to few (oligoarthropathy) to multiple (polyarthropathy) joint involvement

Most common finding: Pannus

– Diffusely thickened hyperechoic or hypoechoic synovium

– Frond-like or nodular synovial proliferation

– May resemble echogenic or hypoechoic synovial fluid

Effusion may be anechoic or hyperechoic

± echogenic speckles due to precipitated fibrin or inflammatory debris

± marginal erosions

– Well-defined, small, periarticular defects

– Coalesce to form larger erosions and more generalized marginal irregularity of joint

– US is more sensitive than radiography and MR at detecting small joint periarticular erosions

– US is less sensitive than contrast-enhanced MR

Color Doppler imaging

– Helpful for estimating level of disease activity and distinguishing synovium from joint fluid

– Hyperemia is more easily appreciated in smaller joints (e.g., hand, wrist, elbow) than larger joints (e.g., shoulder, hip)

– Active pannus leads to increased color flow

– Hyperemia is graded semiquantitatively as high, intermediate, or low/absent vascularity

– Quantitative analysis of hyperemia is feasible, though semiquantitative analysis is adequate for clinical use

Other signs include joint space narrowing, subluxation, deformity, and ankylosis

Coexistent soft tissue features include tenosynovitis, bursitis, and entrapment neuropathy
• Crystal Arthropathy

Always consider in any acute arthritis

Effusion can be anechoic or hyperechoic

Gout results from urate crystal deposition

– 1st metatarsophalangeal joint is 1st affected joint in 50%; later becomes polyarticular

– Best diagnostic clue: Identification of echogenic foci with comet-tail artifacts within and around joint

– ± urate sand (fine punctuate echoes) or sandstorm (larger echogenic aggregates) appearance

– ± urate deposition on articular cartilage surface as thin echogenic band (“urate icing”)

– Soft tophi (no acoustic shadowing) → hard tophi (dense acoustic shadowing)

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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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Joint Effusion

Joint Effusion

Less Common

Helpful Clues for Common Diagnoses

Helpful Clues for Less Common Diagnoses

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Joint Effusion

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