To identify athletes at a higher risk of anterior cruciate ligament (ACL) injury, we developed a video-based screening test focused on hip abductor and rearfoot function. However, age differences in hip or reafoot motion as a contributor to dynamic knee valgus remains unclear. The purpose of this study was to determine how age differences contribute to hip or reafoot motions. Eighty-three female basketball players (41 junior high-school and 42 high-school students) agreed to participate in this study. Participants were measured for hip rotation angle, tibial rotation angle, ankle dorsi-flexion angle, navicular drop and general joint laxity. Subjects also performed single-legged squatting and drop landing from a 30 cm box. Knee-in distance (KID) and Hip-out distance (HOD) were measured using 2-dimensional video images filmed at 30 Hz. Additionally, Dynamic Trendelenburg Test (DTT) and Heel-Floor Test (HFT) were performed. The prevalence of HFT-positive in junior high-school and high-school athletes were not statistically different. DTT-positive during landing was more prevalent in junior high-school athletes than in high-school athletes (P<0.05). Junior high-school athletes demonstrated greater HOD values in squatting than high-school athletes (P<0.05). The range of motion in high-school athletes was significantly greater than in junior high-school athletes in tibial external rotation, hip internal and external rotation (p<0.01). The navicular drop in junior high-school athletes was significantly greater than in high-school athletes (p<0.01), however the navicular height was greater in high-school athletes (p<0.01). Player's age is an important consideration in ACL injury preventative conditioning.

Dynamic knee valgus is considered a risk factor of noncontact ACL injuries. The aim of this study was to determine the association between hip and hindfoot dynamic alignment and dynamic knee valgus.This cross-sectional study involved 88 high school female basketball players (175 legs). Subjects performed single-leg squatting and drop landing which provided a hip-out distance (HOD) and a knee-in distance (KID) via 2D video images. Hip and hindfoot dynamic alignment was evaluated by a dynamic Trendelenburg test (DTT) and a heel-floor test (HFT), respectively, during squatting and landing.The DTT-positive group (dynamic hip mal-alignment with lower non-weightbearing pelvis) demonstrated greater HOD and KID values for both squatting (p＜0.001) and landing (p＜0.001) than the DTT-negative group. The HFT-positive group (5^o or greater hindfoot valgus) demonstrated greater KID values for both squatting (p＜0.01) and landing (p＜0.001), but smaller HOD value for squatting (p＜0.01) than the HFT-negative group.In conclusion, dynamic hip mal-alignment may be associated with both greater HOD and KID, but hindfoot valgus only with greater KID.

This study was performed to establish a simple method to evaluate knee joint proprioception by examining knee-bending angle, in which Lombard's Paradox phenomenon could be confirmed, in 8 extremities of 7 patients with ACL injured who were diagnosed with ACL rupture at a medical facility (ACL injured group) and 10 extremities of 10 healthy adults (control group). As a result, knee joint proprioception in the ACL injured group was significantly lower than that in the control group (P<0.05). Significantly more incidence of Lombard's Paradox phenomenon was confirmed at the knee-extension position in the ACL injured group (P<0.01), compared with the control group. Significant negative correlation was confirmed between the reproductive angle inaccuracy of joint position sensation, a marker of knee joint proprioception, and Lombard's Paradox phenomenon under the conditions of r=-0.58 and the risk rate of 5%. Based on the results of this study, it was suggested that the knee-bending angle, in which Lombard's Paradox phenomenon was confirmed, would be affected by knee joint proprioception through feedback from the ACL mechanoreceptors, and the angle might be used as a simple evaluation method for knee joint proprioception.

The purpose of this study was to determine if there were any reliable predictors for achieving jogging requirements after anterior cruciate ligament (ACL) reconstruction. We analyzed associations among variables collected from 128 subjects at 12 weeks postoperatively, including jogging parameters (i.e. pain, apprehension, speed, and distance), the isokinetic muscle strength of the leg extensors, the knee stability, and patient's profiles (i.e. age, sex, activity level, body mass index (BMI), meniscectomy, and cartilage injury).Jogging parameters were significantly correlated with the isokinetic muscle strength of leg extensors, but not with the knee stability. With the jogging ability of achieving a distance of 2000m at a velicity of 9km/h being an objective variable, a logistic regression analysis revealed that the isokinetic muscle strength of leg extensors and BMI were considered relevant. Using a receiver operating characteristic (ROC) curve analysis and a contingency table, the cut-off values of the isokinetic muscle strength of leg extensors to the uninvolved side and body weight were 85% and 1.9Nm/kg, respectively, whose sensitivity and specificity were 0.90 and 0.82, respectively. Therefore, we concluded that the isokinetic muscle strength of leg extensors is a reliable predictor for projecting the timing to start jogging after ACL reconstruction.

This study examined changes in intra-abdominal pressure and trunk activation during drop jump and the influence of those factors on performance. Intra-abdominal pressure (IAP) and surface electromyography (EMG) activity from the rectus abdominis (RA), transversus abdominis-internal oblique (TrA-IO) and erector spinae (ES) muscles were measured in seven males (22.3±1.0 years) during double-leg drop jumps from a 0.4 m height. Development of IAP (ΔIAP) and normalized rmsEMGs were calculated in the pre-contact, impact and push-off phases, after divided by ground reaction force data. TrA-IO activation which occurred prior to ground contact were the earliest and strongest compared to other muscles activation during each phase.ΔIAP during the impact phase coincided with the peak vertical force. There were significant positive correlations between ΔIAP, TrA-IO activation and vertical force per weight. In addition, the contact time correlated negatively with ΔIAP, TrA-IO activation and vertical force per weight. These findings indicate that ΔIAP and TrA-IO activation may contribute to trunk stability and efficient landing during double-leg drop jump.

Dynamic knee valgus is considered a risk factor of non-contact anterior cruciate ligament (ACL) injury. To identify athletes at a higher risk, we developed a two-dimensional (2D) video-based screening test that determines hip abductor function as well as dynamic hindfoot and knee valgus. The purpose of this study was to validate the accuracy of the indices for dynamic knee valgus derived knee-in distance (KID) and hip-out distance (HOD) from the 2D-video.Twenty healthy university students agreed to participate in this study. Subjects were asked to step off a 30-cm box and land on one leg. This procedure was recorded simultaneously using a 2D video camera in the frontal plane and the Vicon motion capture system. Pearson's correlations examined associations between KID, KID normalized by height (KID/H), HOD, as well as HOD normalized by height (HOD/H) and 3D-valgus (knee valgus) or 3D-IR (tibial internal rotation).Significant correlations were found between the KID and 3D-valgus (r=0.72, p<0.01) and KID/H and 3D-valgus (r=0.73, p<0.01). Associations were not significant between KID and 3D-IR (r=0.08) and between KID/H and 3D-IR (r=0.03). A positive moderate correlation between HOD and 3D-valgus (r=0.46, p<0.05) and HOD/H and 3D-valgus (r=0.50, p<0.05), as well as a negative moderate correlations between HOD and 3D-IR (r=-0.52, p<0.05) and between HOD/H and 3D-IR (r=-0.51, p<0.05) were also observed.We conclude that KID is a reliable alternative for the 3D-valgus and the HOD is for the 3D-valgus and tibial external rotation.

The aim of this study is to investigate the characteristics of pre-existing physical factors associated with the onset of Osgood-Schlatter disease (OSD) in junior soccer players. Fifty-nine junior soccer players of the elementary school were included in this study. The boys who had been diagnosed as OSD were excluded. At the time of the first investigation, the subjects were examined through physical evaluation and an ultrasonography. The subjects were followed up one and a half years, and the tibial tuberosity was classified according to the growth stages using the ultrasonography. After the end of follow-up period, the subjects were divided into two groups, those with signs and symptoms of OSD that appeared during the follow up period and those without that. The Mann-Whitney U test was used for the comparison between OSD group’s and control group’s initial assessments. The players who were followed up for one and half years were 38 people. 5 knees of the 4 players were clinically diagnosed as OSD (OSD group), and the remaining 34 players with no symptoms of the OSD constituted the control group. The range of the bilateral hip external rotation, straight leg raise of the non-dominant side, and knee flexion in the OSD group were significantly lower than those in the control group (p < 0.05). We concluded that a decrease in specific joint flexibility might be related with the onset of OSD.

Dynamic knee valgus is considered a risk factor for anterior cruciate ligament (ACL) injuries. This study identified how knee in distance (KID) and hip out distance (HOD) affect one’s lateral trunk lean (LTL). The results were also tested for reliability. Fifteen female basketball players (30 legs) from a university participated in this study. The participants performed single-leg squats by bending the knee of the supporting leg to 60°. The trials were recorded using a video camera. The KID, HOD, and LTL were measured with two-dimensional images using the Dartfish software, which measured the maximal knee valgus. The Pearson’s correlation coefficient was used to measure the correlation between dynamic knee valgus (KID and HOD) and LTL. Additionally, the Interclass Correlation Coefficient (ICC) was used to measure the reliability of the KID, HOD, and LTL data sets. The statistical significance was established at a level of p<0.05. Results showed that the KID and LTL had a significantly negative correlation, measured at r=-0.227, p<0.05. The ICC (2.1) values were: 0.83 for HOD, 0.99 for KID, and 0.96 for LTL; while the ICC (1.2) values were: 0.86 for HOD, 0.83 for KID, and 0.85 for LTL. The two-dimensional analysis technique revealed that the values were highly reliable. In sum, dynamic knee valgus had a negative correlation with LTL during single-leg squats. Therefore, it was suggested that the factors of dynamic knee valgus might be evaluated using LTL on two-dimensional screening test.