Septic arthritis

Soniya M1*, Dhariniya S2, Ruby Ravichandran3

1Senior Staff Nurse, BMT, Maa Kauvery Hospital, Trichy, Tamil Nadu

2Nursing Educator, Maa Kauvery Hospital, Trichy, Tamil Nadu

3Senior Deputy Nursing Superintendent, Maa Kauvery Hospital, Trichy, Tamil Nadu

*Correspondence

Abstract

Septic arthritis is a serious musculoskeletal infection in children that requires early diagnosis and appropriate treatment to prevent joint destruction, growth disturbances, and long-term functional impairment. Osteomyelitis may occur concurrently with septic arthritis, making accurate clinical assessment, imaging, microbiological investigations, and timely surgical intervention essential. This case report describes an 8-year-old male child weighing 22 kg who presented with a one-month history of pain and swelling of the left knee. Initial Computed Tomography (CT) findings suggested septic arthritis or localized soft-tissue infection, while Magnetic Resonance Imaging (MRI) indicated osteomyelitis involving the medial pole of the patella, with surrounding inflammatory changes and focal cellulitis. The child was admitted for further management and underwent left knee washout and micro drilling of the patella. Intraoperatively, synovial tissue was collected for biopsy, necrotic synovial tissue was debrided, and the joint was irrigated with normal saline. Blood and synovial cultures did not yield bacterial growth. Histopathological examination was reported as suggestive of acute suppurative inflammation. Intravenous antimicrobial therapy, analgesia, postoperative immobilization, and limb elevation were provided. The child improved clinically and was discharged in good general condition with stable vital signs and an orthopedic follow-up appointment.

Key words: Septic arthritis; Initial Computed Tomography (CT); Magnetic Resonance Imaging (MRI)

Introduction

Septic arthritis is an infection of a synovial joint caused by microorganisms, most commonly bacteria. In children, the infection may develop following hematogenous spread or, less commonly, through direct inoculation or extension from adjacent infected tissues. The knee is one of the frequently affected joints. If treatment is delayed, bacterial proliferation and the inflammatory response can damage articular cartilage and surrounding structures, potentially resulting in restricted movement, chronic pain, deformity, and impaired limb function.

Osteomyelitis is an infection involving bone and may coexist with septic arthritis. Infection can spread between adjacent bone, joint, and soft tissues, complicating diagnosis and treatment. Patellar osteomyelitis is relatively uncommon compared with osteomyelitis of the long bones, and its clinical presentation may be nonspecific. Persistent, localized pain and swelling should therefore prompt careful evaluation, particularly when symptoms do not resolve with initial treatment.

According to the Pediatric Infectious Diseases Society and Infectious Diseases Society of America (PIDS/IDSA), suspected bacterial arthritis requires timely clinical assessment, microbiological investigations, appropriate imaging, antimicrobial therapy, and drainage or surgical intervention when indicated. MRI is particularly useful when adjacent osteomyelitis or soft-tissue involvement is suspected. This report describes the clinical presentation, investigations, surgical management, and discharge outcomes of a child diagnosed with septic arthritis of the left knee associated with patellar osteomyelitis.

Case Presentation

An 8-year-old male child presented to the pediatric orthopedics department with a history of pain and swelling of the left knee for approximately one month. The child had initially been evaluated at a nearby hospital, where a CT scan of the left knee revealed findings suggestive of septic arthritis or localized soft-tissue infection. Because of the persistent symptoms and suspected deeper musculoskeletal infection, further evaluation was undertaken. MRI of the left knee demonstrated findings suggestive of osteomyelitis involving the medial pole of the patella, with surrounding inflammatory changes and focal cellulitis.

 

Clinical Findings, Investigation and Diagnosis

The initial CT scan of the left knee suggested septic arthritis or localized soft-tissue infection. Subsequent MRI findings were suggestive of osteomyelitis involving the medial pole of the patella, with surrounding inflammatory changes and focal cellulitis. MRI helped identify the extent of the suspected infection and supported the decision to undertake surgical intervention. Blood investigations showed a coagulation profile within normal limits and non-reactive serological testing. An aerobic blood culture showed no bacterial growth. During surgery, synovial tissue was collected for microbiological culture and histopathological examination. Both aerobic and anaerobic synovial tissue cultures were reported as sterile. Histopathological examination of the synovial tissue showed features suggestive of acute suppurative inflammation, supporting the presence of an acute inflammatory process consistent with the clinical diagnosis.

Management

Postoperatively, the child received intravenous antimicrobial therapy, including Inj.ceftriaxone and Inj.teicoplanin, along with analgesic and supportive treatment. The choice of antimicrobial agents in culture-negative infections should be guided by the suspected pathogens, local antimicrobial susceptibility patterns, clinical response, and infectious diseases consultation. The treating team also recommended proper postoperative Plaster-Of-Paris (POP) care and elevation of the affected limb. Monitoring of the wound, drain output, pain, swelling, distal circulation, sensation, temperature, and overall clinical condition was important during recovery.

Outcome

Following surgical intervention and antimicrobial treatment, the child’s postoperative course was uneventful. The blood and synovial tissue cultures remained negative, while the histopathological findings supported acute suppurative inflammation.

Discharge

At the time of discharge, the child was in good general condition with stable vital signs. No major postoperative complication. Surgical drainage, removal of necrotic tissue, and antimicrobial treatment constituted the principal components of management. The child was discharged with good general condition and stable vital signs.

The orthopedic team advised continued care of the plaster slab, elevation of the affected limb, and adherence to the prescribed medications. The discharge prescription included antimicrobial and symptomatic medications. The family was instructed to seek immediate medical assessment if the child developed fever, increasing pain or swelling, wound redness, pus discharge, or other concerning symptoms. Follow-up was important to assess wound healing, review culture and histopathology findings, determine the need for continued antimicrobial therapy, and plan safe mobilization and rehabilitation.

Conclusion

Septic arthritis associated with osteomyelitis of the patella is an uncommon but potentially serious presentation in children. This case demonstrates the importance of investigating persistent knee pain and swelling even when the child is afebrile. CT and MRI findings helped identify the suspected infection, while operative tissue sampling and histopathological examination provided additional diagnostic information despite negative cultures. Surgical washout, debridement, patellar micro drilling, antimicrobial therapy, and appropriate postoperative care were followed by an uneventful hospital course and discharge in good general condition. Early recognition, multidisciplinary management, and structured follow-up are essential to minimize complications and preserve joint function. Longer-term clinical and functional assessment is required to establish the final outcome.

Reference

  1. Woods, C. R., Bradley, J. S., Chatterjee, A., Copley, L. A., Robinson, J., Kronman, M. P., Lavergne, V. (2021). Clinical practice guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 guideline on diagnosis and management of acute hematogenous osteomyelitis in pediatrics. Journal of the Pediatric Infectious Diseases Society, 10(8), 801–844. https://doi.org/10.1093/jpids/piab027

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