Prepatellar Bursitis – Radiology Board Review
- Clinical: Adults; often males with repetitive kneeling or trauma; anterior knee pain, swelling, erythema, tenderness localized over the prepatellar area; risk factors include occupations requiring frequent kneeling (e.g., housemaids, carpenters); called “housemaid’s knee” from chronic prepatellar bursa irritation
- Etiology/Pathophys: Inflammation of the prepatellar bursa due to repetitive trauma, direct contusion, infection (septic bursitis), or chronic irritation causing accumulation of fluid and inflammatory cells between skin and patella
- Radiograph: Soft tissue swelling anterior to the patella; possible amorphous or punctate calcifications in bursal region; no bony abnormalities or periosteal reaction unless chronic degenerative changes coexist; bony structures usually preserved
- US: Anechoic or hypoechoic fluid collection superficial to the patella with distended prepatellar bursa; possible septations; absence of tendon tears; no Doppler flow within fluid but increased peri-bursal vascularity may be present
- CT: Fluid attenuation collection anterior to patella within prepatellar bursa; soft tissue thickening; absence of bone erosion; may depict complex septated fluid if chronic
- MRI: Oval or lentiform T2 hyperintense fluid collection localized between skin and patella in prepatellar bursa region; may show septations, peripheral enhancement if inflamed; no patellar marrow edema unless concurrent trauma; normal patellar tendon
- Signs: Prepatellar soft tissue swelling indicating bursitis; “Housemaid’s knee” correlates with localized anterior swelling; no classic named imaging signs but fluid collection consistent with bursal distension
- Frameworks: No formal classification system; differentiation into acute vs chronic and aseptic vs septic guided by clinical and lab findings; imaging used to assess extent of fluid and rule out other pathology
- DDx: Septic bursitis (may show increased Doppler flow, clinical signs of infection); prepatellar soft tissue abscess (complex, irregular fluid); cellulitis (diffuse soft tissue edema without defined fluid collection); synovial cyst (different location); tumors (solid mass, irregular borders)
- Tx: Conservative with NSAIDs, rest, avoidance of kneeling in aseptic cases; aspiration for diagnostic and therapeutic purposes; antibiotics if septic; corticosteroid injection in chronic aseptic bursitis; surgical bursectomy if refractory
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