3.1. Patients and Setting
This single-center, retrospective, cross-sectional, descriptive study was conducted at 17 Shahrivar Hospital, a tertiary pediatric care center in Northern Iran. The study included all children aged 1 - 18 years who were admitted to the hospital with a chief complaint of limping between January 2018 and December 2022. Children with limping due to a chronic condition established before the study period and those who were not hospitalized were excluded.
3.2. Data Gathering
Data were retrospectively collected from the electronic medical records of eligible patients. The following information was extracted: demographic data, including age, sex, and place of residence; clinical history, including duration of limping, fever, pain characteristics, associated symptoms, medication history, unpasteurized dairy consumption, trauma history, and respiratory infection in the preceding 15 days; physical examination findings, including localized tenderness, swelling, erythema, joint effusion, range-of-motion limitation, gait abnormality, and temperature; laboratory investigations, including complete blood count (CBC) with white blood cell (WBC) count and differential, CRP, ESR, Wright test, Coombs Wright test, antinuclear antibody, C3, antistreptolysin O, and rheumatoid factor; imaging studies, including plain radiographs of the affected limb and pelvis, ultrasonography of the hip or affected joint, MRI of the affected area, and other imaging modalities when performed; final diagnosis, based on clinical findings, laboratory results, imaging, and response to treatment as recorded in the medical records; and final outcome, classified as complete recovery, incomplete recovery/outpatient follow-up, or complication.
A standardized data collection form was used to ensure consistency. Two independent reviewers extracted the data, and discrepancies were resolved by consensus or by consultation with a senior clinician.
3.3. Diagnostic Definitions and Adjudication
Transient synovitis was defined as acute-onset hip pain or limping with limited range of motion, the absence of systemic infection, and supportive ultrasonographic findings when available. Septic arthritis was defined as clinical suspicion accompanied by laboratory evidence of infection, including elevated inflammatory markers, and/or positive joint aspiration findings, together with the treating physician's final diagnosis. Reactive arthritis was defined as arthritis occurring after a recent infection, without evidence of septic arthritis, and diagnosed by the treating physician based on clinical and laboratory findings. Viral myositis was defined as acute muscle pain or gait disturbance associated with a recent viral illness and elevated muscle enzymes when available. Other diagnoses, including osteomyelitis, Guillain-Barré syndrome, cellulitis, brucellosis, juvenile idiopathic arthritis (JIA), and multisystem inflammatory syndrome in children (MIS-C), were recorded according to the final clinical diagnosis documented by the treating physicians in the hospital records.
3.4. Operational Definitions and Variable Categorization
To ensure clarity and reproducibility, clinical and laboratory variables were defined as follows. Fever was defined as a core body temperature ≥ 38.0°C. Leukocytosis was defined according to age-specific reference ranges (e.g., >15000/μL for infants, >12000/μL for toddlers, and > 10000/μL for older children). Elevated CRP was defined as values > 10 mg/L. Thrombocytosis was defined as a platelet count > 450000/μL. Abnormal ultrasonographic findings included signs of joint effusion, synovial thickening, or other structural abnormalities, as interpreted by the attending radiologist. Symptom duration (limping) was categorized as acute (≤7 days), subacute (>7 days to 4 weeks), and chronic (>4 weeks). Hospitalization outcomes were defined as follows: 1) complete recovery, defined as resolution of symptoms and return to baseline function at discharge; 2) incomplete recovery/outpatient follow-up, defined as ongoing pain or limping requiring further observation and follow-up visits due to unresolved mild symptoms; and 3) complication, defined as the development of secondary issues, such as abscess formation or local soft tissue infection, during or immediately after the hospital stay. These outcomes were based on the final clinical assessment documented by the primary team at discharge.
3.5. Statistical Analysis
Descriptive statistics were used to summarize demographic characteristics, clinical features, laboratory and imaging findings, and the distribution of final diagnoses. Continuous variables are expressed as mean ± standard deviation (SD), and categorical variables are presented as frequencies and percentages, with 95% confidence intervals (CIs) calculated for the prevalence of the main diagnostic categories to enhance reporting robustness. As the study was designed as a descriptive cross-sectional analysis, no formal inferential statistical comparisons, such as P-value comparisons between groups, were performed.