Side-step Cutting using Studded Soccer Boots affects Knee Rotational and Valgus Moments and Injury Potential

Abstract

Clinical and biomechanical research has associated side-step cutting in soccer with non-contact knee injury. Based on critical limits of structures within the knee joint, this study aimed to evaluate the potential for internal rotational and valgus moment and anterior internal joint force changes during side-step cutting as a potential cause of non-contact knee injury in isolation. The recent approval of artificial playing surfaces for competitive matches by the World governing body of soccer (FIFA) prompted this study. PURPOSE: To quantify knee joint internal rotation (M) and valgus (M) moments and anterior internal joint force (F) during side-step cutting using studded soccer boots on a FIFA approved artificial soccer surface. METHODS: Fifteen professional outfield male soccer players participated in the study. All had given written informed consent, were injury-free for at least two seasons and had no history of injury requiring hospital admission. An eight camera retro reflective gait analysis system (120Hz) was synchronised with a force platform (960Hz) to obtain knee joint biomechanical data using 3D inverse dynamics. Each player wore standardised studded soccer boots, whilst undertaking three trials of each manoeuvre on the soccer surface. The trials were a straight line run (0°) and side-step cuts at 30° and 60°. The approach velocity was constrained between 5.5 m-s−1 and 6.0 m-s1 using timing gates. A non-parametric ANOVA was employed to quantify the changes in mean Mz Mv and Fy as a function of cutting angle. RESULTS: Side-step cutting at 30° and 60° resulted in mean Mz and Mv significantly greater than those produced in straight line running (p <0.001). Both knee moments were capable of causing ACL injury in isolation. During 30° and 60° cuts, Mz values were capable of causing cadaveric ACL injury between 8% and 80% of stance. Mv achieved values capable of similar injury between 16% and 5 8% of stance. F did not exceed critical limits for ACL injury throughout the whole of the stance phase. CONCLUSIONS: Side-step cutting at 30° and 60° using soccer boots on an artificial soccer surface approved for use in competitive matches predisposed the knee joint to Mz and Mv which exceeded those required to cause ACL rupture. The ACL appeared to be at greatest risk of injury during 16% to 58% of the stance phase. Compared to previous work, this research has identified biomechanical critical limits for ACL injury are exceeded during soccer side-step cutting when using studded soccer boots on an artificial surface approved for use in competitive matches. As each participant sustained no form of knee injury during testing other factors must play a role in determining ACL injury.