Abstract
The majority of anterior cruciate ligament (ACL) injuries occur during non-contact mechanisms. Knowledge of the risk factors would be relevant to help prevent athletes’ injuries. We aimed to study risk factors associated with non-contact ACL injuries in a population of athletes after ACL reconstruction. From a cohort of 307 athletes, two populations were compared according to the non-contact or contact mechanism of ACL injury. Gender, age and body mass index (BMI) were reported. Passive knee alignment (valgus and extension), knee laxity (KT-1000 test), and isokinetic knee strength were measured on the non-injured limb. The relationship between these factors and the non-contact sport mechanism was established with models using logistic regression analysis for the population and after selection of gender and cut-offs of age, BMI and knee laxity calculated from Receiver Operating Characteristics curve area and Youden index. Age, BMI, antero-posterior laxity, isokinetic knee strength, passive knee valgus and passive knee extension were associated with non-contact ACL injury. According to the multivariate model, a non-contact ACL injury was associated with non-modifiable factors, age (OR: 1.05; p = 0.001), passive knee extension (OR: 1.14; p = 0.001), and with one modifiable factor (Hamstring strength: OR: 0.27; p = 0.01). For women, only passive knee valgus was reported (OR: 1.27; p = 0.01). Age, passive knee extension and weak Hamstring strength were associated with a non-contact ACL injury. Hamstring strengthening could be proposed to prevent ACL injury in young male athletes or in case of knee laxity.
Highlights
Every year, several hundred thousand anterior cruciate ligament (ACL) reconstructions following a sports injury are performed in the world [1–3]
Knee anatomy measured by X-ray or Magnetic Resonance Imaging, such as a decreased femoral intercondylar Notch width or an increased medial or lateral tibial plateau slopes are known as risk factors of non-contact mechanisms of ACL injury [8,17–20]
A significant difference was found between the 2 groups for the following qualitative variables: age, weight, Body Mass Index (BMI), quadriceps and hamstring strength at 60 and 180◦ /s, passive knee valgus, passive knee extension and knee laxity, and they were included in the binary logistic regression model (Table 2)
Summary
Several hundred thousand ACL reconstructions following a sports injury are performed in the world [1–3]. Several risk factors have been identified to explain non-contact ACL injuries [6–11] These risk factors are classified into two distinct categories: extrinsic or environmental ), and intrinsic, inherent to the individual (anatomic, neuromuscular, biomechanical, physiological, psychological and genetic factors) [4,8,10] In this latter category, some risk factors are modifiable (e.g., body weight or muscle strength) or not (e.g., anatomical knee structure, joint laxity) because they can or cannot be controlled by the individual to reduce the ACL injury risk [10]. In the non-modifiable intrinsic risk factors, female gender and youth age (>14 or ≤20 years old) are identified as risk factors of non-contact ACL rupture [12–16]. Passive knee extension (recurvatum) and anterior-posterior knee laxity seem to be risk factors for the occurrence of a non-contact ACL injury, especially in women [13,21–25]
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