A 5-year-old boy is brought to the emergency department by his parents due to fever and knee pain. The patient was diagnosed with streptococcal pharyngitis 2 weeks ago and treated with a 10-day course of amoxicillin. Two days ago, he developed fever and fatigue and started eating and drinking less than usual. Today, he cries every time he bends his right knee, and he refuses to walk. Temperature is 39.4 C (102.9 F). On examination, the patient appears tired but alert and is reading a book with his father. The right knee is swollen and tender to palpation. The patient holds the knee in a flexed position and has pain with passive range of motion. Laboratory results are as follows: X-ray of the right knee shows joint effusion and soft tissue swelling. Which of the following is the best next step in management of this patient?

Question

A 5-year-old boy is brought to the emergency department by his parents due to fever and knee pain.  The patient was diagnosed with streptococcal pharyngitis 2 weeks ago and treated with a 10-day course of amoxicillin.  Two days ago, he developed fever and fatigue and started eating and drinking less than usual.  Today, he cries every time he bends his right knee, and he refuses to walk.  Temperature is 39.4 C (102.9 F).  On examination, the patient appears tired but alert and is reading a book with his father.  The right knee is swollen and tender to palpation.  The patient holds the knee in a flexed position and has pain with passive range of motion.  Laboratory results are as follows:  X-ray of the right knee shows joint effusion and soft tissue swelling.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_d6d2_34f3_bc81_5d8b516a742c_MD0003_00 This patient's fever, right knee pain and swelling, and refusal to bear weight in the setting of leukocytosis, elevated inflammatory markers (C-reactive protein, erythrocyte sedimentation rate), and joint effusion on x-ray are concerning for septic arthritis. Septic arthritis is a bacterial joint infection that results from hematogenous seeding by bacteria or, less commonly, from local extension from infected skin or bone. The next step in management is arthrocentesis to obtain synovial cultures and confirm the diagnosis. Purulent synovial fluid with >50,000/mm³ leukocytes is consistent with septic arthritis. After blood and synovial cultures are obtained, empiric parenteral antibiotics are administered to target the most likely pathogens (Staphylococcus aureus, streptococci). Antibiotics preceding cultures can interfere with isolation of the offending organism and lead to false-negative results. Due to the risk of permanent joint destruction, prompt surgical drainage will likely be required to decompress the joint space and remove infectious debris. (Choice B) Intraarticular corticosteroids treat joint pain and swelling due to inflammatory arthritis (eg, juvenile idiopathic arthritis, psoriatic arthritis). Inflammatory arthritis is present ≥6 weeks in contrast to this patient's acute presentation; however, it is unlikely to cause a unilateral monoarticular arthritis with high fevers. (Choice C) MRI is sensitive for the detection of septic arthritis but requires sedation in young children and should not delay urgent arthrocentesis. If the patient remains febrile or fails to improve after arthrocentesis and 48 hours of appropriate antibiotic therapy, MRI should be performed to evaluate for concomitant osteomyelitis. (Choice D) Penicillin, along with nonsteroidal anti-inflammatory drugs, is the treatment of choice for rheumatic fever (RF). RF can result from untreated group A streptococcal pharyngitis; this child's pharyngitis was treated appropriately. In addition, the arthritis associated with RF is migratory rather than monoarticular. (Choice E) Rest and nonsteroidal anti-inflammatory drugs are appropriate for transient synovitis, which typically presents with joint pain and decreased range of motion in a child following a viral illness. However, high fever, leukocytosis, and elevated inflammatory markers are red flags for septic arthritis. (Choice F) Rheumatoid factor assay is typically positive in patients with rheumatoid arthritis, which is rare in children and presents with chronic joint pain and stiffness. Educational objective: Septic arthritis should be suspected in children with acute onset of fever and joint pain and swelling. Management includes arthrocentesis, empiric parenteral antibiotics, and prompt surgical drainage. References: Transient synovitis, septic hip, and Legg-Calvé-Perthes disease: an approach to the correct diagnosis. (http://www.ncbi.nlm.nih.gov/pubmed/25439014) Pediatric septic arthritis. (http://www.ncbi.nlm.nih.gov/pubmed/28336043)

A 5-Year-Old Boy Is Brought to the Emergency Department by His