Acute limb pain in young children presenting to the emergency department (ED) can be a sign of serious pathology, with septic arthritis being the most important condition to rule out. Two clinical decision rules (CDRs) have been developed to assist with the diagnosis: Kocher's rule (which allocates points for fever, weight-bearing status, white cell count and erythrocyte sedimentation rate) and Caird's rule (which also includes C-reactive protein). This study aimed to determine (1) the diagnostic accuracy of the two rules for the identification of septic arthritis and (2) other clinical features most strongly associated with septic arthritis.

Prospective observational study of consecutive children aged <16 years with non-traumatic acute limp presenting to three EDs in Melbourne, Australia between July 2016 and September 2018. Data were prospectively collected on weight-bearing status, duration of symptoms, joint examination findings and signs of systemic disease. Structured chart reviews and telephone follow-up were used to adjudicate the presence/absence of septic arthritis. Area under the receiver operating characteristics curve (AUC) was calculated for each published CDR, and sensitivity, specificity and likelihood ratios were calculated for clinical findings.

Of 583 patients presenting with atraumatic limp, 535 (91.8%) eligible patients had sufficient follow-up data. 14 (2.6%) were diagnosed with septic arthritis. Kocher's rule had an AUC of 0.72 (95% CI 0.42 to 1.00), while Caird's rule had an AUC of 0.78 (95% CI 0.52 to 1.00) for septic arthritis. Univariable analysis demonstrated strong associations between range of joint motion (unadjusted OR 13.9, 95% CI 5.0 to 38.5), signs of systemic disease (OR 20.5, 95% CI 6.2 to 67.7), hip pain (OR 3.8, 95% CI 1.2 to 11.7) and presence of fever (OR 5.1, 95% CI 1.0 to 25.1) with septic arthritis. Markedly reduced range of motion compared with the unaffected side had the highest positive likelihood ratio (12.1, 95% CI: 7.5 to 19.5), while inability to weight bear had a positive likelihood ratio of 3.85 (95% CI 2.49 to 5.95). None of the tested clinical findings had a negative likelihood ratio less than 0.3, or a positive predictive value of more than 25%.

Septic arthritis is a relatively uncommon diagnosis in children presenting to the ED with an acute limp. Markedly reduced range of motion and inability to weight bear appear to be the strongest predictors of septic arthritis; however, their absence is insufficient to rule out the diagnosis.

Correct diagnosis and treatment of septic arthritis (SA) are essential to achieve satisfactory results and avoid lifelong consequences. Diagnosing septic arthritis is not always easy, which is why new biomarkers have been sought. Another difficulty in diagnosis is the increase in septic arthritis due to Kingella Kingae, which does not show the same signs and symptoms as classic Staphylococcus aureus infections. Increasingly, magnetic resonance imaging plays a more fundamental role in diagnosing septic arthritis, and many studies are focused on this line, especially for the study of associated pathologies. Numerous studies have been published on less invasive treatments for septic arthritis, although the evidence suggests that the results should be taken cautiously. Although most of the published studies focus on the hip and knee, there have also been recent publications on SA in the upper limb, foot, and ankle. Finally, the literature also pays attention to SA in young children due to its different etiology and the greater difficulties in its diagnosis.

Acute non-traumatic limp in children has many causes, ranging from common benign and self-limiting disease to serious time-sensitive emergencies such as septic arthritis. We aimed to (1) describe the epidemiology and workup of paediatric acute non-traumatic limp presentation in three Australian EDs and (2) compare investigations and treatment between a tertiary paediatric centre and two non-tertiary centres.

A retrospective chart review of children aged 0-16 years, with an initial presentation of non-traumatic limp to three EDs in Melbourne, Australia. Data on presentation, management and outcomes was systematically collected on all eligible patients.

Of 63 941 presentations over a 12-month period, 475 (0.7%) met inclusion criteria. The median (IQR) age of presentation was 5 (3-8) years, with a male predominance (61%). Blood tests and imaging were performed in 39% and 51%, respectively. 34% of presentations had no investigations. The most frequent ED diagnoses were transient synovitis (37%) and viral myositis (16%). 84% were discharged home after ED evaluation. Compared with the two non-tertiary hospitals, children who presented to the tertiary centre were less likely to have any investigation performed (OR=0.41, 95% CI: 0.27 to 0.62, p<0.001) and more likely to be discharged home after evaluation (OR=4.67, 95% CI: 2.79 to 7.81, p<0.001).

Although mostly due to benign disorders, an important number of limping children who presented to the ED had serious disease, with approximately one-third of these not diagnosed at the initial ED visit. There is large variation in workup including blood test, imaging and decisions regarding ED disposition.

Transient synovitis (TS) is a common and benign cause of hip pain in children, but must be distinguished from more serious entities such as septic arthritis, osteomyelitis, and pyomyositis. Our objectives were to determine the risk of missed bacterial musculoskeletal infection and rates of diagnostic testing in children diagnosed with TS.

We performed a cohort study using the Pediatric Heath Information System of children 1-10 years diagnosed with TS in the ED. We determined rates of missed bacterial musculoskeletal infection (defined as a new diagnosis of septic arthritis, osteomyelitis, or pyomyositis within 14 days of initial ED visit). We described the initial diagnostic evaluation and ED management of children diagnosed with TS and variability between sites.

We analyzed 6419 encounters from 37 hospitals. 62 (1.0%, 95%CI: 0.7-1.2%) children were diagnosed with a missed bacterial musculoskeletal infection. Children with missed infection were younger than those without (median age 2.6 vs. 4.6 years, p < 0.01). Serum laboratory testing was performed in 76% of encounters with minimal variation across sites. There was significant variation in the rates of hip ultrasound by site (2 to 92%), which has increased in use over time (from 42% in 2016 to 62% in 2021).

In this large observational study, missed bacterial musculoskeletal infection in children diagnosed with TS was rare but more common in younger children. The optimal combination of bloodwork and radiographic testing, especially ultrasound, to distinguish TS from more serious disease remains unclear.

Acute septic arthritis in children is an orthopaedic emergency. A delay in diagnosis and inappropriate treatment can result in devastating damage to the joint with lifelong disability as a consequence. The clinical presentation can be a diagnostic challenge, especially in young children. A recent systematic review showed that joint tenderness and fever are important signals of septic arthritis. Ultrasound is helpful in detecting the presence of a joint effusion. Plain radiographs may show bone changes but magnetic resonance imaging is the most reliable imaging study for detecting concomitant osteomyelitis. The diagnosis of acute septic arthritis is highly suggestive when pus is aspirated from the joint, in case of a positive culture or a positive gram stain of the joint fluid, or if there is a white blood-cell count in the joint fluid of more than 50000/mm3. Staphylococcus aureus is the most commonly cultured organism. Recent systematic reviews have identified the most effective drainage techniques, including needle aspiration, arthroscopy and arthrotomy, depending on the affected joint. After the drainage procedure it is important to monitor the clinical and laboratory outcomes. Additional drainage procedures may be necessary in select cases.

This case series evaluates the performance of a point-of-care ultrasonography (POCUS) decision-support algorithm for the diagnosis of transient synovitis in the pediatric emergency department (ED).