Paraarticular Cystic Mass

DIFFERENTIAL DIAGNOSIS

Common

• Ganglion Cyst
• Baker Cyst
• Parameniscal Cyst
• Bursal Distension
• Liquefied Hematoma
• Abscess or Collection

Less Common

• Cystic-Looking Soft Tissue Tumors
• Pseudoaneurysm

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

• Establish whether mass is intra- or extracapsular

If extracapsular, does mass communicate with joint?

Where does mass communicate with joint?

Does it attach to labrum or meniscus, or does it communicate with other part of joint?

Sometimes direct continuity with joint is not visible, but mass can be seen pointing toward joint

– Passive movement of joint may occasionally be helpful to more clearly visualize communication

Helpful Clues for Common Diagnoses

• Ganglion Cyst

Mucinous fluid contained within fibrous pseudocapsule

– Not lined by synovial tissue

Results from extruded synovial fluid

– Joint pathology (e.g., synovitis) can occur within ganglia but is uncommon due to closed or limited communication

Most common around wrist/hand and foot

– 80% of soft tissue masses of wrists/hands and feet

– Dorsal wrist ganglia are more commonly symptomatic, although volar wrist ganglia are overall more common

Typical locations reflect weakness in joint capsule

– Dorsal radiocarpal joint, particularly scapholunate joint

Can impinge upon distal end of posterior interosseous nerve

– Scapho-trapezio-capitate joint

Near A1 pulley on middle, index, and ring fingers

– Does not appear to communicate with metacarpophalangeal joint or flexor tendon sheath

Anechoic, well-defined, rounded or irregular mass alongside joint

– ± comet-tail artifacts due to aggregates of colloid material

– Infrequently hyperechoic, due to hemorrhage or inflammatory content from joint

Typically has neck pointing toward particular joint

– Usually neck cannot be traced to joint as too small

– Relevant to identify potential joint of origin as this will aid surgical exploration

Most ganglia per se are not painful with pain induced by ganglion leakage

– Pay particular attention to any inflammation or free fluid around ganglion

50% of ganglia recur after percutaneous aspiration

– Not possible to determine viscosity of content on grayscale appearances alone

– Leakage of cyst content can cause pain for 24-36 hours after aspiration

– Hyaluronidase may facilitate aspiration by making contents less viscous
• Baker Cyst

Semimembranous-gastrocnemius bursa, which communicates with joint

– Slit-like opening in capsule close to root of posterior horn medial meniscus

Classic talk-bubble configuration on transverse US with beak of bubble emerging between semimembranous tendon and medial head gastrocnemius muscle

– Slight knee flexion during scanning can accentuate this communication

– Frequently bilateral

Usually extends distally over medial belly gastrocnemius muscle

– Less commonly spreads proximally and uncommonly spreads into semimembranous or gastrocnemius muscle

Has synovial membrane and therefore affected by synovial processes (e.g., PVNS) involving knee joint

– Any pathological process in knee can be seen in Baker cyst

Prone to either hemorrhage or leakage

– May make Baker cyst symptomatic

Hemorrhage

– Increased speckled echogenicity of cyst fluid

Leakage or rupture

– Free fluid around margin of cyst

– Angulated arrow-like, rather than rounded, configuration of cyst

– ± pericystic inflammation
• Parameniscal C yst

Cystic mass extending from peripheral aspect of meniscus

Usually associated with horizontal meniscal tear

– Mucinous content (from synovial fluid) expressed as parameniscal cyst

Occasionally, no meniscal tear is present

– Meniscal tear may have healed

– Cyst may have arisen from severe myxoid degeneration of meniscus in absence of tear

Meniscal myxoid content expressed as parameniscal cyst

Percutaneous cyst aspiration is helpful, particularly in cases without visible meniscal tear
• Bursal Distension

2 types of bursae

Synovial bursae: Synovial-lined bursa, which occur at defined anatomical locations

– Prone to synovial disorders, such as synovitis or synovial osteochondromatosis

Adventitial bursae: Non-synovial-lined bursae acquired due to friction between opposing structures

Some paraarticular bursa more prone to bursitis than others

Subacromial-subdeltoid bursa

– Attached to coracoacromial ligament and greater tuberosity distal to tendon insertions

– Distension strongly associated with rotator cuff tear

– If bursal wall thickened ± hyperemia, consider inflammatory arthropathy (e.g., SLE, RA) or infection

Olecranon bursa

– Between olecranon process and skin

– Common site of gouty bursitis

– Commonly inflamed, not commonly infected

Iliopsoas bursa

– Anterior to femoral head between hip capsule and iliopsoas muscle/tendon

– Communicates with hip joint in 15% of patients

– Consider iliopsoas infection, particularly tuberculous

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Tags: Diagnostic Ultrasound Musculoskeletal

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

DIFFERENTIAL DIAGNOSIS

Common

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

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Paraarticular Cystic Mass

Paraarticular Cystic Mass

Less Common

Helpful Clues for Common Diagnoses

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Paraarticular Cystic Mass

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