Background: Musculoskeletal infection is a major cause of morbidity in the pediatric population. Despite the canonical teaching that an irritable joint and signs of infection likely represent an infected joint space, recent evidence in the pediatric hip has demonstrated that alternative diagnoses are equally or more likely and that combinations of pathologies are common. The knee is the second most commonly infected joint in children, yet there remains a paucity of available data regarding the epidemiology and workup of the infected pediatric knee. The authors hypothesize that there is heterogeneity of pathologies, including combinations of pathologies, that presents as a potentially infected knee in a child. The authors aim to show the utility of magnetic resonance imaging and epidemiologic and laboratory markers in the workup of these patients.
Methods: A retrospective review of all consults made to the pediatric orthopaedic surgery team at a single tertiary care center from September 2009 through December 2015 regarding a concern for potential knee infection was performed. Excluded from the study were patients with penetrating trauma, postoperative infection, open fracture, no C-reactive protein (CRP) within 24 hours of admission, sickle cell disease, an immunocompromised state, or chronic osteomyelitis.
Results: A total of 120 patients were analyzed in this study. There was marked variability in pathologies. Patients with isolated osteomyelitis or osteomyelitis+septic arthritis were older, had an increased admission CRP, were more likely to be infected with Staphylococcus aureus, required an increased duration of antibiotics, and had an increased incidence of musculoskeletal complications than patients with isolated septic arthritis.
Conclusions: When considering a child with an irritable knee, a heterogeneity of potential underlying pathologies and combinations of pathologies are possible. Importantly, the age of the patient and CRP can guide a clinician when considering further workup. Older patients with a higher admission CRP value warrant an immediate magnetic resonance imaging, as they are likely to have osteomyelitis, which was associated with worse outcomes when compared with patients with isolated septic arthritis.
Level of evidence: Level III-retrospective research study.
Osteomyelitis is Commonly Associated With Septic Arthritis of the Shoulder in Children.J Pediatr Orthop. 2017 Dec;37(8):547-552. doi: 10.1097/BPO.0000000000000709. J Pediatr Orthop. 2017. PMID: 26691242
The impact of the current epidemiology of pediatric musculoskeletal infection on evaluation and treatment guidelines.J Pediatr Orthop. 2008 Oct-Nov;28(7):777-85. doi: 10.1097/BPO.0b013e318186eb4b. J Pediatr Orthop. 2008. PMID: 18812907
Septic arthritis in children: frequency of coexisting unsuspected osteomyelitis and implications on imaging work-up and management.AJR Am J Roentgenol. 2015 Jun;204(6):1289-95. doi: 10.2214/AJR.14.12891. AJR Am J Roentgenol. 2015. PMID: 26001240
Bone and Joint Infections in Children: Septic Arthritis.Indian J Pediatr. 2016 Aug;83(8):825-33. doi: 10.1007/s12098-015-1816-1. Epub 2015 Jul 21. Indian J Pediatr. 2016. PMID: 26189923 Review.
Acute haematogenous community-acquired methicillin-resistant Staphylococcus aureus osteomyelitis in an adult: case report and review of literature.BMC Infect Dis. 2012 Oct 25;12:270. doi: 10.1186/1471-2334-12-270. BMC Infect Dis. 2012. PMID: 23098162 Free PMC article. Review.