Frontal Plane Angles Research Articles

Reliability and Validity of the Articulation Motion Assessment System Using a Rotary Encoder

This study aimed to validate the effectiveness of the Articulation Motion Assessment System (AMAS), a joint kinematic evaluation system, for clinical applications. AMAS enables synchronised measurement using neurophysiological indicators, overcoming laboratory setting limitations. We compared AMAS-based ankle joint kinematic evaluations, particularly the sagittal and frontal plane angles, with two-dimensional (2D) motion analysis to determine the validity and reliability of AMAS. Both AMAS and 2D motion analysis reliably detected significant differences in angles within the sagittal and frontal planes. Correlation analysis revealed a significant moderate-to-strong correlation between the AMAS and the conventional method of 2D motion analysis, proving the measurement validity of the AMAS (ρ = 0.53–0.77 for sagittal plane angles; ρ = 0.46–0.72 for frontal plane angles). The average root mean squared error (RMSE) was significantly lower in AMAS (10.90 ± 2.93° for sagittal plane angles; 13.44 ± 1.09° for frontal plane angles) than in the inertial sensor-based three-dimensional (3D) motion analysis. Reliability analysis revealed high reliability of measurements (intraclass correlation coefficients (ICC) ≥ 0.76). However, the Bland–Altman analysis identified a slightly lower fixed bias, which was observed as a characteristic of each measurement system. The AMAS accurately detects ankle joint angles without being constrained by measurement environment limitations. Synchronised measurements using neurophysiological indicators potentially contribute to understanding ankle joint control mechanisms and developing rehabilitation strategies.

Do Different Next-to-Skin Garments Change Thermal Sensation, Jump Height and Landing Knee Valgus After Cold Exposure?

Exposure to the cold can negatively affect muscle performance. This study compared the effects of two different full-length, lower body, next-to-skin garments on thermal sensation, countermovement jump (CMJ) height and knee frontal plane angle upon landing following cold exposure against a control. After familiarisation, 13 male and 11 female recreationally active adults attended three separate laboratory testing sessions where a randomly assigned next-to-skin garment was used (compression, thermal and control (shorts)). A pre- and post-testing protocol comprising CMJ and drop landings interspersed with a sedentary cooling period of 40 min at 0 °C was adopted. High-speed motion analysis and subjective ratings of thermal sensation were recorded. Exposure to the cold significantly reduced thermal sensation (p < 0.001) scores and CMJ height (p < 0.001). Only female participants felt significantly warmer (p ≤ 0.009) in the next-to-skin garments. Losses in CMJ height were significantly reduced by the next-to-skin garments compared to the control with the thermal garment producing better results. There was little change in knee frontal plane angle upon landing in all the garments tested. Ambient cooling at 0 °C for 40 min had a significant effect on CMJ height and thermal sensation but not knee valgus upon landing. Participants in winter sports should consider next-to-skin garments in conjunction with proper warm-ups and re-warming techniques to protect themselves from the negative effects of the cold.

Differences in landing biomechanics in the presence of delayed onset muscle soreness following or not active recovery

ObjectiveDelayed onset muscle soreness (DOMS) can reduce joint range of motion and strength, cause edema, and increase joint stiffness. Here we set out to determine whether quadriceps DOMS followed by an active recovery low-intensity exercise alters jump landing biomechanics. Methods3D landing kinematics, kinetics, and DOMS were evaluated in 26 healthy adults (15 women) performing drop and vertical jump landings before and after a squat protocol to induce quadriceps DOMS. In the presence of DOMS, half of the participants (n = 13) performed a low-intensity exercise for active recovery (10-minute treadmill walking), while the other half (n = 13) did not. Descriptive statistics and generalized estimative equations were applied to determine the effects of DOMS and active recovery on landing kinematics and kinetics. ResultsDOMS decreased knee and ankle flexion angles and increased knee and ankle frontal plane angles during vertical jumps. DOMS elicited a longer time to reach peak ground reaction force during drop jumps. Low-intensity exercise for active recovery reduced DOMS perception but did not alter the biomechanics of landing. ConclusionDOMS changes landing strategy. However, including a low-intensity exercise for active recovery before landing practice did not change the kinematics and kinetics of landing.

Examining spinal mobility, aerobic capacity and functional movement in patients with non-specific chronic low back pain: a case-control study

Background/Aims The increasing cost and incidence of non-specific chronic low back pain means that many physiotherapists are reconsidering the management of this condition. The primary aim of this study was to examine spinal mobility, aerobic capacity and functional movement screen in patients with non-specific chronic low back pain. The secondary aim was to determine the factors affecting the disability level. Methods Participants aged between 18–65 years old diagnosed with non-specific chronic low back pain for >3 months were recruited as a study group, while those without low back pain in the last 3 months were the control group. Outcome measures included the Functional Movement Screen for functional movement, the 2-Minute Step Test for aerobic capacity, the Spinal Mouse for spinal mobility and Oswestry Disability Index for disability level. Results A total of 60 participants, 30 people with non-specific chronic low back pain (42.7 ± 10.6 years) and 30 people without low back pain (42.0 ± 7.3 years), were included in this study. There were statistically significant differences in the total sagittal plane angle (P<0.001), total frontal plane angle (P=0.03), 2-Minute Step Test (P<0.001) and Functional Movement Screen (P<0.001) scores between groups. Pain and aerobic capacity explained 42.4% of the variance as determinants of disability in the study group. Conclusions In people with non-specific chronic low back pain, sagittal and frontal plane range of motion and aerobic capacity were decreased and their functional movements were impaired. Pain intensity and aerobic capacity affect the disability level of non-specific chronic low back pain. Implications for practice People with non-specific chronic low back pain have reduced spinal mobility, aerobic capacity and functional movement. These parameters should be included when determining treatment programmes. At the same time, the level of disability can be reduced by decreasing pain intensity and increasing aerobic capacity of people with low back pain.

Interlaboratory Study Toward Combining Gait Kinematics Data Sets of Long-Distance Runners.

The limited sample size in gait studies has hampered progress in the field. This challenge could be addressed through multicenter studies, thereby leveraging data sets from different laboratories. This study compared 3-dimensional lower-extremity running kinematics between the Biomechanics and Motor Control Laboratory, Federal University of ABC (Brazil), and the Running Injury Clinic, University of Calgary (Canada). Three-dimensional lower-extremity kinematics from 23 male runners were collected from each laboratory using comparable instrumentation and experimental procedures. The 3-dimensional hip, knee, and ankle angles were compared within and between centers using root-mean-square deviation. Two-sample t tests Statistical Parametric Mapping tested the hypothesis that the data from both laboratories were not different. The sagittal plane hip, knee, and ankle angles were similar between laboratories, while notable differences were observed for frontal (hip and ankle) and transverse (hip and knee) plane angles. The average interlaboratory root-mean-square deviation (2.6°) was lower than the intralaboratory root-mean-square deviation (Biomechanics and Motor Control = 4.8°, Running Injury Clinic = 5.6°), with the ankle transverse angle displaying the smallest, and the knee transverse angle displaying the largest variability. This study demonstrates the potential of combining gait kinematics data from different laboratories to increase sample size, but frontal and transverse plane data should be considered with caution.

Comparison of joint kinematics from optical marker-based and inertial sensor-based motion capture during change-of-direction movements

The development of inertial measurement units (IMUs) has opened up possibilities to test kinematics of sports movements in natural environments (Di Paolo et al., 2023). This advantage over lab-based optical motion capture (OMC) comes at the cost of inherent inaccuracies. Especially, fast multidirectional movements including de- and accelerations pose a challenge for inertial-based movement reconstruction with limited task-specific validation research available (Heuvelmans et al., 2022). Therefore, we aimed to test the validity of IMU-based kinematics in a 180° change of direction (COD) task to provide insight into the applicability for future on-field ACL injury risk research. Twenty-six sports science students were equipped with eight IMU sensors of the Noraxon Ultium Motion System and an adaption of the Plug-in-Gait markerset (53 markers) recorded by a VICON OMC system. They performed five 180° anti-clockwise CODs at their maximum speed. As an example for sagittal and frontal plane angles relevant for ACL injury risk, the knee flexion and abduction angle at the initial contact of the cutting step (right leg) were calculated using the Noraxon MyoMotion software for IMU-recorded data and OpenSim for marker-based OMC data. At the time of abstract submission, the data of five (randomly chosen) participants had been analysed. More participants and more joint angle outcomes will be included in follow-up analyses. Deviations between IMU-generated and OMC-generated joint angles are depicted in Figure 1. Within subjects, deviations below 1.5 standard deviations were observed. Between subjects, deviations ranged from 0° and 22° in knee flexion angles and 0° and 11° in knee abduction angles. A general trend towards higher joint angles measured by the IMU system is noticeable, suggesting a possible off-set error. For four out of five participants, the knee flexion deviation was below 10°, which can be considered an accuracy which is tolerable but requires consideration in the interpretation (< 2°: good accuracy, 2-5°: acceptable accuracy, 5-10°: tolerable accuracy, > 10° unbearable accuracy; Bessone et al., 2022). Deviations in knee abduction angles appear too large given the small physiological joint range and motion in this plane. This preliminary analysis of individual deviations suggests acceptable deviations between IMU and OMC measurements regarding knee flexion but problematic deviations for knee abduction. Prospectively, we aim to investigate possible off-set corrections, e.g. through a better alignment of the underlying biomechanical models, and alternative approaches for IMU-based movement reconstruction, e.g. through optimal control simulations (Nitschke et al., 2024).

The Effect of Static Trial on Knee Adduction Moment During Walking.

Background and aim Sophisticated technologies in rehabilitation, such as three-dimensional gait analysis, allow for measuring kinematic and kinetic variables while performing activities. The first peak external knee adduction moment (EKAM) is considered an important outcome in individuals with knee osteoarthritis (OA) and has been shown to be affected by changes in foot position in static trials. The present study aimed to explore the variables in static trials that may lead to changes in the value of the EKAM while walking. Methods Twelve individuals participated in the current study and were asked to perform three static trials as follows: 20° toe-out, straight (0°), and 20° toe-in. The participants were asked to walk five trials (their own shoes and paces). The first peak EKAM was the main study outcome and was compared between conditions. Linear regression was used to investigate which variables in the static trials significantly predicted the magnitude of change in the EKAM while walking. Results The first peak EKAM significantly decreased by 8.2% while walking when changing the foot position in static trials from 20° toe-in to 20° toe-out. The magnitude of change in the EKAM was significantly (p<0.01) predicted by the magnitude of change in the knee joint frontal plane angle, shank transverse plane angle, ankle joint frontal plane angle, and hip joint frontal plane angle during static trials between 20° toe-in and 20° toe-out. The model was able to predict 94% of the variation in the EKAM due to changes in foot position during static trials. Conclusion Modifications in foot position during static trials led to a change in the first peak EKAM while walking. Researchers should focus on controlling the knee joint frontal plane angle, shank transverse plane angle, ankle joint frontal plane angle, and hip joint frontal plane angle during static trials when conducting longitudinal or crossover studies. Controlling these variables is necessary to reduce the likelihood of the EKAM being affected by static trials and to ensure that the EKAM changes in dynamic trials are not masked or increased by static trials.

The effects of core muscle fatigue on lower limbs and trunk during single-leg drop landing: A comparison between recreational runners with and without dynamic knee valgus

BackgroundA deficit in neuromuscular trunk control can impact the lower limb motion, predisposing runners to injuries. This deficit may show a greater impact on runners with dynamic knee valgus. This study aimed to compare the effect of core fatigue on kinetic, kinematic, and electromyographic parameters of the trunk and lower limbs during single-leg drop landing between runners with and without dynamic knee valgus. MethodsTwenty-seven recreational runners were allocated to the valgus (n = 14) and non-valgus groups (n = 13). They performed the test before and after a fatigue protocol, taking a step forward and landing on the force platform while maintaining balance. The fatigue protocol included isometric and dynamic exercises performed consecutively until voluntary exhaustion. The vertical ground reaction force, the sagittal and frontal plane angles, and the electromyographic activity were evaluated. The integral of electromyographic activity was calculated into three movement phases. ANOVA with repeated measures was used to verify the group, time, and interaction effects. ResultsAfter fatigue, both groups showed a significant reduction in the minimum (p = 0.01) and maximum (p = 0.02) knee angles in the frontal plane (more dynamic knee valgus) and greater gluteus medius activity (p = 0.05) from the peak of knee flexion to the end of the movement. The valgus group had a greater hip excursion (p = 0.01) and vertical linear shoulder displacement (p = 0.02) than the non-valgus. ConclusionOur results suggest that core fatigue can impact the local muscle and the distal joint and that the groups presented different strategies to deal with the demand during landing.

The relationship of hip strength and dynamic knee valgus during single leg squat in physically active females

BackgroundSingle leg squat (SLS) is an important motion commonly observed in sports. Excessive dynamic knee valgus (DKV) during SLS may increase non-contact knee injury risks particularly in physically active females. As muscular strength plays crucial role in controlling DKV, the present study aims to evaluate the correlation between hip strength and knee frontal plane angle during SLS among females with and without excessive DKV. MethodsThirty-four volunteers were allocated to the valgus (n = 17) and non-valgus (n = 17) groups. Their motions during SLS at 45° and 60° knee flexion were captured and analyzed using three-dimensional motion analysis system. Isokinetic hip strength was examined at 180°/s in flexion, extension, abduction, and adduction for both legs. Pearson's correlation test was computed to evaluate the relationship between hip strength and knee angle during SLS. FindingsNon-dominant hip extensor strength (r = −0.56, p = 0.02) and dominant hip adductor strength (r = −0.51, p = 0.04) were significantly related to the knee frontal plane angle during 45° SLS among those without DKV. Meanwhile, those with DKV showed a significant relationship between the knee frontal plane angle for both legs and non-dominant hip abductor strength during 60° SLS. InterpretationBoth groups demonstrated the relationship of hip strength on knee frontal plane angle during SLS, whereby increased hip strength may minimize excessive DKV. Those with excessive DKV should train to strengthen their hip abductor to reduce knee valgus particularly during deep squats.

Movement Quality Assessment of Army Reserve Officers' Training Corps Cadets: A Report of Validity and Normative Data.

Movement quality screening in early-career military populations, like Army Reserve Officers' Training Corps (AROTC) cadets, could decrease the negative impact of musculoskeletal injury observed within the military. Movement quality screening techniques should be valid before being pursued in the field. Normative data describing movement quality of AROTC cadets are also needed. Therefore, the aims of this study were to determine criterion validity of several movement quality assessments and report normative jump-landing kinematics of AROTC cadets. This cross-sectional research was approved by the Institutional Review Board. As part of a larger study, 20 AROTC cadets (21.3 ± 3.4 years; 1.7 ± 0.1 m; 73.8 ± 14.8 kg) had 3-dimensional (3D) and 2-dimensional (2D) kinematic data collected simultaneously while performing a jump-landing task. Variables of interest were 3D hip and knee sagittal, frontal, and transverse joint angles at maximum knee flexion. An experienced rater calculated sagittal and frontal 2D joint angles at maximum knee flexion. Averages of 2D and 3D angles were calculated to describe normative data and for further data analysis. Bivariate correlations between 3D and 2D variables were used to determine criterion validity. Moderate correlations were found between 2D and 3D hip frontal plane angles (P = .05, r =-0.33), 2D and 3D knee sagittal plane angles (P = .04, r = 0.35), and 2D and 3D knee frontal plane angles (P = .03, r = -0.36). Normative values of knee and hip kinematics demonstrated averages of 17.58° of knee adduction, 16.48° of knee external rotation, 11.57° of hip abduction, 10.76° of hip internal rotation, and 103.47° of knee flexion during landings. However, ranges demonstrated that landing patterns vary within AROTC cadets. The normative values of 3D jump-landing kinematic data indicate that movement quality varies greatly within AROTC cadets, and some cadets display potentially injurious movements. Therefore, screening movement quality could be beneficial to determine musculoskeletal injury risk in AROTC cadets. Based on the correlations discovered in this study, we recommend the 2D techniques used in this study be researched further as they may serve as alternatives to expensive, timely 3D techniques that could be better utilized in military environments.

The applicability of markerless motion capture for clinical gait analysis in children with cerebral palsy

The aim of this comparative, cross-sectional study was to determine whether markerless motion capture can track deviating gait patterns in children with cerebral palsy (CP) to a similar extent as marker-based motion capturing. Clinical gait analysis (CGA) was performed for 30 children with spastic CP and 15 typically developing (TD) children. Marker data were processed with the Human Body Model and video files with Theia3D markerless software, to calculate joint angles for both systems. Statistical parametric mapping paired t-tests were used to compare the trunk, pelvis, hip, knee and ankle joint angles, for both TD and CP, as well as for the deviation from the norm in the CP group. Individual differences were quantified using mean absolute differences. Markerless motion capture was able to track frontal plane angles and sagittal plane knee and ankle angles well, but individual deviations in pelvic tilt and transverse hip rotation as present in CP were not captured by the system. Markerless motion capture is a promising new method for CGA in children with CP, but requires improvement to better capture several clinically relevant deviations especially in pelvic tilt and transverse hip rotation.

The Force-Vector Theory Supports Use of the Laterally Resisted Split Squat to Enhance Change of Direction.

Cooley, C, Simonson, SR, and Maddy, DA. The force-vector theory supports use of the laterally resisted split squat to enhance change of direction. J Strength Cond Res 38(5): 835-841, 2024-The purpose of this study was to challenge the conventional change of direction (COD) training methods of the modern-day strength and conditioning professional. A new iteration of the modified single-leg squat (MSLS), the laterally resisted split squat (LRSS), is theorized to be the most effective movement for enhancing COD performance. This study lays out a rationale for this hypothesis by biomechanically comparing the LRSS, bilateral back squat (BS), and MSLS with a COD task (90-degree turn). One repetition maximum (1RM) for LRSS, MSLS, and BS was measured for 23 healthy active female subjects. Peak ground reaction forces (GRF) for the dominant leg were recorded when performing COD and the LRSS, MSLS, and BS at 70% 1RM. Peak frontal plane GRF magnitude and angle were calculated for each task and submitted to repeated measures ANOVA. Peak GRF magnitude was significantly larger for COD (2.23 ± 0.62 body weight) than the LRSS, MSLS, and BS (p ≤ 0.001). Peak GRF angle was not significantly different between COD and the LRSS (p = 0.057), whereas the MSLS and BS (p < 0.001) vector angles were significantly greater than COD. In this application of the force-vector theory, the LRSS more closely matches COD than the MSLS or BS. Thus, the LRSS has the greater potential to enhance COD.

Biomechanical Balance Measures During Timed Up and Go Test Improve Prediction of Prospective Falls in Older Adults

ObjectiveTo assess the feasibility of using biomechanical gait balance measures, the frontal and sagittal plane center of mass (COM)-Ankle angles, to prospectively predict recurrent falls in community-dwelling older adults. DesignA cohort study with a 1-year longitudinal follow-up. Logistic regression was used to test the ability of the COM-Ankle angles to predict prospective falls. SettingGeneral community. ParticipantsSixty older adults over the age of 70 years were recruited using a volunteer sample. InterventionsNot applicable. Main Outcome Measure(s)Biomechanical balance parameters: the sagittal and frontal plane COM-Ankle angles during the sit-to-walk and turning phases of the timed Up and Go test. The COM-Ankle angles are the inclination angles of the line formed by the COM and lateral ankle (malleolus) marker of the stance foot in the sagittal and frontal planes. We also included the following clinical balance tests in the analysis: Activity-Specific Balance Confidence, Berg Balance Scale, Fullerton Advanced Balance scale, and timed Up and Go test. Their abilities to predict falls served as a reference for the biomechanical balance parameters. ResultsWhen the biomechanical gait balance measures were added to all the confounders, the explained variance was increased from 25.3% to 50.2%. Older adults who have a smaller sagittal plane COM-Ankle angle at seat-off, a greater frontal plane COM range of motion during STW and a smaller frontal plane angle during turning were more likely to become recurrent fallers. Conclusion(s)Our results indicated that dynamic biomechanical balance parameters could provide valuable information about a participant's future fall risks beyond what can be explained by demographics, cognition, depression, strength, and past fall history. Among all biomechanical parameters investigated, frontal plane COM motion measures during STW and turning appear to be the most significant predictors for future falls.

Design and evaluation of a 3D printed mechanical balancer for soft tissue balancing in total knee replacement

PurposeSoft tissue balancing is an important step in a total knee procedure, carried out manually, or using an indicator. The purpose of this study was to evaluate our design of 3D printed Balancer, and demonstrate how it could be used at surgery. ProceduresWhen inserted between the femur and tibia, the Balancer displayed the forces acting across the lateral and medial compartments, indicated by pointers at the end of the handle. A loading rig was used to measure the pointer deflections for different forces applied at different locations on the condyle surfaces. Repeatability and reproducibilty were evaluated. The Balancer was tested in six fresh knee specimens using a surgical simulation rig. Main findingsPointer deflections of up to 12 millimeters occurred for less than 1 mm displacements at the condyle surfaces. Reproducibility tests showed a standard deviation of 14% at lower loads, reducing to only 4% at higher loads. Mean pointer deflections were within 8% for forces applied at ±10 mm AP, and +5/−3 mm in an ML direction, relative to the neutral contact point. In specimens, most lateral to medial force differences could be corrected by a 2° change in frontal plane angle of the tibial resection. Effects of ligament releases were also demonstrated. Principal conclusionsThe 3D printed Balancer was easy to use, and provided the surgeon with lateral and medial force data over a full range of flexion, enabling possible corrective procedures to be specified.

Lower extremity coordination strategies to mitigate dynamic knee valgus during landing in males and females

Frontal and sagittal plane landing biomechanics differ between sexes but reported values don’t account for simultaneous segment or joint motion necessary for a coordinated landing. Frontal and sagittal plane coordination patterns, angles, and moments were compared between 28 males and 28 females throughout the landing phase of a drop vertical jump. Females landed with less isolated thigh abduction (p = 0.018), more in-phase motion (p < 0.001), and more isolated shank adduction (p = 0.028) between the thigh and shank in the frontal plane compared with males. Females landed with less in-phase (p = 0.012) and more anti-phase motion (p = 0.019) between the thigh and shank in the sagittal plane compared with males. Females landed with less isolated knee flexion (p = 0.001) and more anti-phase motion (p < 0.001) between the sagittal and frontal plane knee coupling compared with males. Waveform and discrete metric analyses revealed females land with less thigh abduction from 20 % to 100 % and more shank abduction from 0 to 100 % of landing, smaller knee adduction at initial contact (p = 0.002), greater peak knee abduction angles (p = 0.015), smaller knee flexion angles at initial contact (p = 0.035) and peak (p = 0.034), greater peak knee abduction moments (p = 0.024), greater knee abduction angles from 0 to 13 % and 19 to 30 %, greater knee abduction moments from 19 to 25 %, and smaller knee flexion moments from 3 to 5 % of landing compared with males. Females utilize greater frontal plane motion compared with males, which may be due to different inter-segmental joint coordination and smaller sagittal plane angles. Larger knee abduction angles and greater knee adduction motion in females are due to aberrant shank abduction rather than thigh adduction.

Foot rotation and pelvic angle correlate with knee abduction moment during 180° lateral cut in football players

BackgroundLateral movements are challenging for 2D video-analysis and are therefore often omitted in functional tests for Anterior Cruciate Ligament (ACL) injury risk assessment. The purpose of the present study was to investigate the association between frontal and transverse plane angles obtained from 2D video-analysis and knee abduction moment (KAM) from gold standard 3D motion capture in a 180° lateral cut task. The hypothesis was that 2D angles other than the knee joint effectively explain variations in KAM. MethodsThirty-four healthy football players (age 22.8 ± 4.1 years) performed a series of 180° lateral cut (lateral shuffles) tasks. The peak KAM was collected through a 3D motion capture system. A 2D video-analysis movement assessment identified frontal and transverse plane joint kinematics: foot projection angle (FPA), Frontal Plane Knee Projection Angle (FPKPA), Pelvis tilt angle (PA), and Trunk tilt angle (TA). A forward stepwise regression model was used to assess significant 2D predictors of KAM (p < 0.05). ResultsFPA and PA were the only significant predictors (R2-ajdusted = 9.2%, p < 0.001), with external foot rotation and contralateral pelvic drop associated with higher KAM. Based on the regression model, the “High FPA & PA group” was defined and showed higher KAM than the rest of the cohort (p = 0.012, ES = 0.71). ConclusionsThe external foot rotation and the contralateral pelvic drop from 2D video-analysis were associated with higher peak KAM during the 180° lateral cut. A qualitative assessment of the 180° lateral cut could offer precious insights on ACL injury risk mitigation. Level of EvidenceDescriptive Laboratory Study.

Video Analysis of 26 Cases of Second ACL Injury Events in Collegiate and Professional Athletes.

Significant effort has gone into the identification and quantification of the underlying mechanisms of primary ACL injury. Secondary ACL injury is observed in approximately 1/4 to 1/3 of athletes who return to sport following ACL reconstruction. However, little has been done to evaluate the mechanisms and playing circumstances surrounding these repeat injuries. The purpose of this study was to characterize the mechanisms of non-contact secondary ACL injuries using video analysis. It was hypothesized that in video recordings of secondary ACL injury, athletes would exhibit greater frontal plane hip and knee angles, but not greater hip and knee flexion, at 66 ms following initial contact (IC) as compared to at IC and 33ms following IC. Cross-Sectional Study. Twenty-six video recordings of competitive athletes experiencing secondary ACL ruptures via noncontact mechanisms were analyzed for lower extremity joint kinematics, playing situation, and player attention. Kinematics were assessed at IC as well as 33 ms (1 broadcast frame) and 66 ms (2 broadcast frames) following IC. Knee flexion and knee frontal plane angles were greater at 66 ms than IC (p ≤ 0.03). Hip, trunk, and ankle frontal plane angles were not greater at 66 ms than IC (p ≥ 0.22). Injuries were distributed between attacking play (n=14) and defending (n=8). Player attention was most commonly focused on the ball (n=12) or an opponent (n=7). A single-leg landing accounted for just over half of the injuries (54%), while a cutting motion accounted for the remainder of the injuries (46%). Secondary ACL injury was most likely to occur during landing or a sidestep cut with player attention external to their own body. Knee valgus collapse combined with limited hip motion was identified in the majority of secondary injuries. Level IIIb.

Relationship Between Age and Running Kinematics in Female Recreational Runners.

Sex-based analyses are important when studying running kinematics. Females experience a unique aging process and demonstrate differences in running biomechanics from males. The purpose was to determine the relationship between age and running kinematics in female runners. Forty-six female runners (18-65y) ran at self-selected jogging and maximal speed on a treadmill. Lower-extremity joint kinematics were calculated, and 2 principal component analyses (jogging speed and maximal speed) were performed from kinematic variables. Regression was used to examine the relationship between age and identified components, and between age and the variables with the highest loadings within these components. For jogging speed, there was a positive relationship between age and ankle varus at initial contact and a negative relationship between age and peak eversion, hip adduction, knee flexion, dorsiflexion, and hip adduction at initial contact (Ps < .05). For maximal speed, initial contact ankle frontal plane angle became more positive with age, and there was a negative relationship with age and peak eversion, dorsiflexion and knee flexion, and knee flexion and hip adduction at initial contact (Ps < .05). Primarily distal joint angles decreased with increasing age in female recreational runners at self-selected running speeds.

Validity of an artificial intelligence, human pose estimation model for measuring single-leg squat kinematics

Few studies have investigated the validity of 2D pose estimation models to evaluate kinematics throughout a motion and none have included adolescents. Adolescent athletes completed single-leg squats while 3D kinematic data and 2D sagittal and frontal plane videos were recorded. Sagittal and frontal plane joint motion throughout the single-leg squats and angles at peak knee flexion were compared among 2D pose estimation, 3D motion analysis, and traditional 2D motion analysis techniques. Statistical parametric mapping compared waveforms while Pearson’s correlation compared the relationships of joint angles at peak knee flexion among techniques, respectively. We observed significant waveform differences between 2D pose estimation and 3D motion analysis at the beginning and end of the squat for sagittal plane hip and knee motion, for most of the squat for frontal plane hip motion, and throughout the entire squat for sagittal plane ankle motion and frontal plane pelvic motion. We observed moderate-to-strong relationships (r = 0.68-0.94) for sagittal plane joint angles between 2D pose estimation and 3D techniques. We observed fair correlations (r = 0.53-0.54) for frontal plane pelvic and hip joint angles between 2D pose estimation and 3D motion analysis. We observed poor relationships for the frontal plane knee angle between 3D motion analysis with 2D pose estimation (r = 0.20) and traditional 2D motion analysis (r = 0.05), respectively, but observed a strong relationship (r = 0.95) between the 2D techniques. 2D pose estimation is a valid alternative to 3D motion analysis and traditional 2D motion analysis for evaluating most sagittal and frontal plane angles during a single-leg squatting task.

Assessment of normal radial joint orientation angles in nonchondrodystrophic small-breed dogs.

To establish reference intervals for radial joint orientation angles in the frontal and sagittal planes in small-breed dogs and to compare them to those previously reported for medium- and large-breed dogs. Antebrachii of 30 skeletally mature, nonchondrodystrophic small-breed dogs were evaluated radiographically. Orthogonal radiographs were retrospectively assessed to determine the anatomic medial proximal radial angle, anatomic lateral distal radial angle, anatomic cranial proximal radial angle (aCrPRA), and anatomic caudal distal radial angle (aCdDRA). The frontal plane angle, θ angle, and procurvatum were also calculated. The radial joint orientation angles determined were compared to those previously reported for medium- and large-breed dogs via a 1-sample t test. Mean and SD values for anatomic medial proximal radial angle, anatomic lateral distal radial angle, aCrPRA, and aCdDRA were 80.86 ± 2.86°, 85.60 ± 1.74°, 87.99 ± 2.79°, and 83.08 ± 3.14°, respectively. The mean and SDs for frontal plane angle, θ angle, and procurvatum were 4.75 ± 2.46°, 11.88 ± 1.76°, and 16.79 ± 4.13°, respectively. aCrPRA and aCdDRA were significantly different when compared to previously reported radial joint angles for medium- and large-breed dogs. Reference intervals for small-breed dog radial joint orientation angles were reported. Significant differences were identified for some joint orientation angles when compared to medium- and large-breed dogs. This small-breed reference interval reported can be utilized in planning of radial angular limb deformity corrective surgery, particularly when dogs are bilaterally affected.