# Floating Knee Severity Score (FKS): A Novel Multidimensional Prognostic Model for Predicting Functional Outcomes After Floating Knee Injuries

## TL;DR

This study introduces a new scoring system to predict long-term outcomes for patients with floating knee injuries, helping doctors make better treatment decisions.

## Contribution

The FKS-score is the first multidimensional prognostic model specifically for floating knee injuries.

## Key findings

- The FKS-score accurately predicts functional outcomes with an AUC of 0.89.
- A score of ≥9 points identifies patients at high risk for poor outcomes with 78% sensitivity and 85% specificity.
- Variables like vascular injury and Gustilo classification significantly influence prognosis.

## Abstract

Purpose: Floating knee (FK) injuries are complex high-energy traumas associated with poor functional outcomes. This study aimed to identify independent predictors of functional prognosis and to develop a novel, multidimensional scoring system to predict long-term functional outcomes. Methods: A retrospective analysis was performed on 182 adult patients with ipsilateral femur and tibia fractures treated between January 2010 and December 2023. Functional outcomes were assessed using the Karlström–Olerud criteria and dichotomized as excellent–good versus fair–poor. Variables significant in univariate analysis were entered into a multivariate logistic regression model. Independent predictors were used to construct the FKS-score. Predictive performance was evaluated using ROC analysis. Results: Of the 182 patients, 103 (56.6%) achieved excellent–good outcomes, while 79 (43.4%) had fair–poor results. Multivariate analysis identified Fraser IIA–B (OR 2.12), Fraser IIC (OR 3.85), Gustilo I–II (OR 1.42), Gustilo IIIA–B (OR 2.61), Gustilo IIIC (OR 3.22), segmental fractures (OR 2.18), extensor mechanism injury (OR 2.04), vascular injury (OR 4.89), intra-articular extension (OR 1.92), and patella fracture (OR 1.76) as independent predictors of poor functional outcome. The FKS-score, ranging from 0 to 15, demonstrated high predictive accuracy (AUC = 0.89). An optimal cut-off value of ≥9 points yielded a sensitivity of 78% and specificity of 85%. Conclusions: The FKS-score is the first comprehensive prognostic scoring system specifically developed for floating knee injuries. It provides a reliable, practical tool for early risk stratification and the prediction of long-term functional outcomes, thereby supporting clinical decision-making and patient counseling.