A case report on non-specific synovitis of the knee due to septic foreign body in the Hoffa fat pad causing diagnostic dilemma

INTRODUCTION & IMPORTANCE: Recurrent chronic synovitis due to foreign body is a rare entity and it may progress into chronic septic arthritis. Chronic recurrent synovitis or septic arthritis may leave permanent damage to the articular cartilage and renders the child with permanent disabilities. CASE PRESENTATION: A 03-year-old girl has been transferred to a tertiary centre with a history of recurrent pain and swelling of the right knee and on and off limping for six weeks duration. These symptoms were preceded by a history of prick injury to the ipsilateral knee. CLINICAL FINDINGS & INVESTIGATIONS: The knee was warm to the touch, moderately tender and contains effusion. C-Reactive peptide level series were elevated, Erythrocyte sedimentation rate was 83 mm/1 st hour and White cell count was 10,300/mm3. The ultrasonography revealed suprapatellar bursitis, other investigations such as Antinuclear antibody levels, Rheumatoid factor and Bacterial culture of the aspirate were negative. INTERVENTIONS & OUTCOME: Arthrotomy and synovectomy performed. While performing synovectomy, an organic thorn has been retrieved from the Hoffa fat pad. The child was treated with intravenous antibiotics for ten days (Co-amoxiclav) and discharged. Her recovery was uneventful and in six weeks she has shown marked improvement of the knee function. Histological examination revealed non-specific chronic synovitis. RELEVANCE & IMPACT: Chronic synovitis due to foreign body mimicking septic arthritis or causing diagnostic difficulty is a rare entity in the paediatric population. Careful clinical evaluation after creating a good rapport with the child is of utmost importance.