Open Access Highly Accessed Research article

Biomechanical and functional indicators in male semiprofessional soccer players with increased hip alpha angles vs. amateur soccer players

Matthias Lahner1*, Christoph von Schulze Pellengahr1, Philipp Alexander Walter1, Carsten Lukas2, Andreas Falarzik3, Kiriakos Daniilidis4, Lars Victor von Engelhardt5, Christoph Abraham6, Ewald M Hennig6 and Marco Hagen6

Author Affiliations

1 Department of Orthopaedic Surgery, Ruhr-University Bochum, St. Josef-Hospital, Gudrunstr. 56, 44791 Bochum, Germany

2 Department of Diagnostic and Interventional Radiology and Nuclear Medicine, Ruhr-University Bochum, St. Josef-Hospital, Gudrunstr. 56, 44791 Bochum, Germany

3 Olympic Training Center Westfalen/Bochum, Hollandstr. 95, 44866 Bochum, Germany

4 Department of Orthopaedic Surgery, Annastift Hannover, (Medical School Hannover, MHH), Anna-von-Borries-Str. 1-7, 30625 Hannover, Germany

5 Faculty of Health Sciences, University of Witten/Herdecke, Alfred-Herrhausen-Str. 50, 58448 Witten, Germany

6 Biomechanics Laboratory, Department of Sport and Movement Sciences, University of Duisburg-Essen, Gladbecker Str. 182, 45141 Essen, Germany

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BMC Musculoskeletal Disorders 2014, 15:88  doi:10.1186/1471-2474-15-88

Published: 16 March 2014



Femoroacetabular impingement (FAI) is predominant in young male athletes, but not much is known about gait differences in cases of increased hip alpha angles. In our study, the hip alpha angle of Nötzli of soccer players was quantified on the basis of magnetic resonance imaging (MRI) with axial oblique sequences. The aim of the current study was to compare the rearfoot motion and plantar pressure in male semiprofessional soccer players with increased alpha angles to age-matched amateur soccer players.


In a prospective analysis, male semiprofessional and amateur soccer players had an MRI of the right hip to measure the alpha angle of Nötzli. In a biomechanical laboratory setting, 14 of these participants in each group ran in two shoe conditions. Simultaneously in-shoe pressure distribution, tibial acceleration, and rearfoot motion measurements of the right foot were performed.


In the semiprofessional soccer group, the mean value of the alpha angle of group was 55.1 ± 6.58° (range 43.2-76.6°) and 51.6 ± 4.43° (range 41.9-58.8°) in the amateur group. In both shoe conditions, we found a significant difference between the two groups concerning the ground reaction forces, tibial acceleration, rearfoot motion and plantar pressure parameters (P < 0.01, P < 0.05, P = 0.04). Maximum rearfoot motion is about 22% lower in the semiprofessional group compared to the amateur group in both shoe conditions.


This study confirmed that semiprofessional soccer players with increased alpha angles showed differences in gait kinematics compared to the amateur group. These findings support the need for a screening program for competitive soccer players. In cases of a conspicuous gait analysis and symptomatic hip pain, FAI must be ruled out by further diagnostic tests.

Rearfoot motion; Tibial acceleration; Alpha angle of Nötzli; Femoroacetabular impingement; Magnetic resonance imaging; Soccer players