Introduction

Variations from neutral lower extremity alignment can have long term consequences on the musculoskeletal health of an athlete. Genu varum is associated with a higher prevalence of knee pathologies, such as meniscal tears, patellofemoral syndrome and ultimately osteoarthritis. Previous research has identified increased genu varum in athletes and in soccer players of all levels. However, no studies to date have specifically investigated the radiographic lower extremity alignment of elite soccer players. Our aim was to define the normal range of lower extremity alignment in a cohort of elite male soccer players. We hypothesized that professional soccer players have increased genu varum as compared to controls.

Methods

Full lower extremity leg length alignment anteroposterior (AP), AP knee, and 45-degree posteroanterior knee (Rosenberg) radiographs were reviewed from professional male soccer players. Hip-Knee Angle (HKA), Medial Proximal Tibia Angle (MPTA), Lateral Distal Femur Angle (LDFA), degree of tibial bowing, degree of femoral bowing, and Medial Neck Shaft Angle (MNSA) were measured on alignment radiographs. The interbone distance between the distal femur and proximal tibia was measured in millimeters on the knee AP and Rosenberg radiographs. A cohort of age and sex matched controls was selected and radiographic measurements were obtained for comparison. As the data was determined to be normally distributed, statistical analyses were performed using unpaired t-tests with the P value set at 0.05.

Results

32 male elite soccer players were included in the cohort. There was no statistical difference in age between the soccer athletes and the control cohort. The soccer athletes had significantly more varus alignment then controls (2.9 ? 3 versus 0.4 ? 2.3, P<0.001). Additionally, soccer players had significantly smaller MPTA and smaller femoral MNSAs than the controls did. Soccer professionals also had significantly smaller interbone distance than controls in the medial compartment on Rosenberg radiographs but significantly smaller interbone distance in both compartments on AP radiographs.

Discussion

We demonstrated that a cohort of male professional soccer athletes have an increased degree of genu varum as compared to age and sex matched controls. While the contribution to genu varum is likely multifactorial, it seems probable that proximal tibia (MPTA) and proximal femur (MNSA) alignment contribute to this phenomenon. The observed decreased joint space in the medial compartment on Rosenberg radiographs as compared to controls is consistent with previous hypotheses that genu varum in athletes is secondary to increased activity and narrowing of the joint space. However, our findings that MPTA and MNSA in the athletes were significantly lower from controls indicates that skeletal alignment factors contribute to the observed genu varum. What remains unknown is if varus alignment develops due to increased load over time or if a varus alignment is a beneficial trait resulting in increased performance in the athlete. We are the first to examine professional soccer athletes radiographically for leg length alignment and have aimed to establish what the “normal” is for these elite athletes. Future longitudinal investigations could help determine causal relationship for genu varum and what the long-term risk for injury is.