# The association between patellar malalignment and Osgood–Schlatter disease in children

## TL;DR

This study found that patellar malalignment, measured by the Insall–Salvati index, is strongly linked to Osgood–Schlatter disease in children, especially when combined with high BMI and exercise levels.

## Contribution

The study identifies the Insall–Salvati index as a strong independent predictor of Osgood–Schlatter disease in children.

## Key findings

- High Insall–Salvati index (ISI) values were strongly associated with Osgood–Schlatter disease (OSD) with an odds ratio of 16.13.
- The optimal cutoff value for ISI to predict OSD was 1.14, with an AUC of 0.933, outperforming BMI as a predictor.
- Male gender, high BMI, and high exercise levels were also identified as independent risk factors for OSD.

## Abstract

The aim of this study was to investigate the association between patellar position [assessed by the Insall–Salvati index (ISI)] and Osgood–Schlatter disease (OSD) in children, and to evaluate the predictive value of ISI and body mass index (BMI) for OSD.

A case–control/cross-sectional study was conducted enrolling 127 children aged 10–16 years between March 2023 and June 2025, including 76 children with OSD (observation group) and 51 healthy children (control group). ISI values were measured radiographically, and data on BMI, visual analog scale score, gender, and recent exercise level were collected. Univariate analysis and multivariate logistic regression were used to analyze associated factors, and the predictive performance of ISI and BMI was evaluated using receiver operating characteristic (ROC) curves.

The observation group had significantly higher ISI values, BMI values, and proportion of males compared to the control group (all P < 0.05). Multivariate logistic regression identified that the male gender (OR = 5.61), high BMI (OR = 1.77), high ISI (OR = 16.13), and recent high exercise level (OR = 7.03) were independent risk factors for OSD (all P < 0.05). ROC curve analysis indicated that the area under the curve (AUC) for ISI predicting OSD was 0.933 (optimal cutoff value 1.14), superior to the AUC for BMI (0.793).

The ISI value is a strong independent indicator associated with OSD, with an optimal cutoff value of 1.14. The pathogenesis of OSD may involve the combined effects of abnormal biomechanics (high ISI) and mechanical load (high BMI and high exercise level). Early screening of ISI may help identify high-risk individuals for targeted prevention.