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Description

Prepatellar bursitis is a common cause of anterior knee pain and swelling and may present with erythema, warmth, and limited motion. When infection is present, distinguishing septic bursitis from cellulitis or septic arthritis can be clinically challenging. Aspiration and culture of bursal or joint fluid remain the diagnostic gold standard; however, overlying cellulitis and concern for deeper spread of infection may limit the safety of these procedures. Point-of-care ultrasound (POCUS) is increasingly recognized as a rapid, noninvasive imaging modality in the emergency setting that allows visualization of superficial bursae, adjacent soft tissues, and joint spaces. This case demonstrates the critical role POCUS has in guiding diagnostic and procedural decision-making in suspected septic bursitis, particularly when aspiration is relatively contraindicated. This case highlights the use of

A 31-year-old man with a history of ulcerative colitis on immunomodulatory therapy presented to urgent care with two days of right anterior knee pain and swelling following recreational soccer. He denied direct trauma and was afebrile but unable to bear weight, prompting referral to the emergency department. Examination revealed warmth, erythema, and swelling localized to the prepatellar region with preserved knee extension and limited flexion. Laboratory studies demonstrated leukocytosis, elevated erythrocyte sedimentation rate, and markedly elevated C-reactive protein. Bedside musculoskeletal ultrasound revealed a hypoechoic fluid collection within the prepatellar bursa with internal debris and surrounding soft tissue changes consistent with cellulitis, without evidence of intra-articular effusion. These findings supported a diagnosis of septic prepatellar bursitis with overlying cellulitis and reduced concern for septic arthritis.

This case demonstrates how point-of-care ultrasound can rapidly distinguish septic prepatellar bursitis from septic arthritis and cellulitis in an immunosuppressed patient with acute knee swelling. By confirming bursal involvement and excluding intra-articular effusion, POCUS directly guided safe procedural decision-making and avoided unnecessary arthrocentesis. Early integration of ultrasound into the evaluation of musculoskeletal infections can improve diagnostic confidence, optimize management, and support timely, patient-centered care.

Publication Date

5-8-2026

Disciplines

Emergency Medicine

Comments

2026 Research Day Corewell Health West, Grand Rapids, MI, May 8, 2026. Abstract 1967

Utilization of Ultrasound for Rapid Diagnosis and Management of Knee Septic Bursitis Overlayed with Purulent Cellulitis: A Case Report

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