Risk factors and their interactions for knee pain in female volleyball athletes: A cross-sectional study

Background Chronic knee pain is a common problem in volleyball athletes. Interaction of those risk factors are not well understood, especially in females. The aim of this study was to establish gender specific reference values for risk factors, their relative importance for knee pain and their interaction in female volleyball players (n = 62). Methods Range of motion (ROM) of dorsiflexion, knee flexion and hip joint was assessed with a mobile application and strength values of hip and knee were measured with an isokinetic dynamometer (ISOMED2000). Information gain of variables on knee pain were determined and interaction between variables were accessed with association rules including discretization. Results Foot posture index (FPI) and dorsiflexion ROM have the highest information gain, followed by hip internal ROM and external rotation ROM as well as hip abduction strength. Based on discretization following categories have a high occurrence of knee pain: FPI > 3, dorsiflexion ROM < 41°, knee flexion ROM (< 136°), hip internal rotation ROM < 38°, hip external rotation strength < 0.8 Nm/kg, hip abduction strength < 1.4 Nm/kg. Association rules revealed that quadriceps strength is only important if dorsiflexion ROM is below 41° and should exceed 3.6 Nm/kg. High FPI values combined with low ROM such as dorsiflexion (70%), knee flexion (75%) and hip internal rotation (80%) increase likelihood of knee pain. Furthermore, interactions between low strength and ROM increase likelihood of knee pain (100%). Conclusion We conclude, that the combination of categories with high occurrence of knee pain leads to an even further increased likelihood of knee pain, which does not happen in low risk-categories. In order to prevent knee pain various deficits should be prevented in order to minimize the chances of knee pain.