Shoulder External Over Internal Rotation Ratio Is Related to Biomechanics in Collegiate Baseball Pitching.

Altering baseball pitching mechanics affects both performance and the risk of injury. The purpose of this study is to investigate the relationships of shoulder external over internal rotation ratio (SEIR) and other shoulder rotational properties during physical exam and biomechanics of pitching for 177 collegiate baseball pitchers. The shoulder range of motion was quantitatively measured using a custom-made wireless device. Pitching motion data were collected at 240 Hz, and a custom program was created to calculate the throwing arm motion and loading during baseball pitching. Linear regression and analysis of variance tests were performed to investigate the relationships between the shoulder physical exam outcomes and throwing arm biomechanics. SEIR had significant correlations with shoulder horizontal adduction angle at foot contact, maximum shoulder external rotation angle, maximum shoulder linear velocity, and elbow angle at ball release. SEIR groups had significant differences in shoulder proximal force, adduction torque, internal rotation torque, and horizontal adduction torque, and in elbow medial force and varus torque. Glenohumeral internal rotation deficit and total rotational motion deficit had no relationships with throwing arm motions or joint loadings. Shoulder health should be monitored to improve understanding of pitching mechanics in collegiate baseball pitchers.

Open Foot Stance Reduces Lead Knee Joint Loading During Golf Swing.

Foot stance and club type's relationship with lead knee joint biomechanics and possible involvement with injury incidences in amateur golfers have not been evaluated. This study included 16 male right-handed amateur golfers who performed golf swings with 2 different foot stances (straight and open) using 4 different club types (driver, 3 iron, 6 iron, and 9 iron) while standing on 2 force plates in a motion capture laboratory. A custom program calculated the kinematics and kinetics of the lead knee. Overall, the open stance reduced most translations, rotations, forces, and torques of the lead knee in all 4 club types when compared with the straight stance. The open stance reduced the rotation motion (-28%), compressive force (-5%), and rotation torque (-9%) when compared with the straight stance, which are the highest contributors to grinding of cartilage. The driver club had significantly larger values in most translations, rotations, forces, and torques when compared among the 4 club types. The open stance reduced the rotation motion, compressive force, and rotation torque in the lead knee joint compared with the straight stance. Lead knee joint biomechanics should be monitored to reduce injury in amateur golfers.

Patellofemoral Joint Loading during the Performance of the Wall Squat and Ball Squat with Heel-to-Wall-Distance Variations.

INTRODUCTION: Although bodyweight wall and ball squats are commonly used during patellofemoral rehabilitation, patellofemoral loading while performing these exercises is unknown, which makes it difficult for clinicians to know how to use these exercises in progressing a patient with patellofemoral pathology. Therefore, the purpose was to quantify patellofemoral force and stress between two bodyweight squat variations (ball squat vs wall squat) and between two heel-to-wall-distance (HTWD) variations (long HTWD vs short HTWD). METHODS: Sixteen participants performed a dynamic ball squat and wall squat with long HTWD and short HTWD. Ground reaction force and kinematic data were used to measure resultant knee force and torque from inverse dynamics, whereas electromyographic data were used in a knee muscle model to predict resultant knee force and torque, and subsequently, all these data were inputted into a biomechanical computer optimization model to output patellofemoral joint force and stress at select knee angles. A repeated-measures two- and three-way ANOVA ( P < 0.01) was used for statistical analyses. RESULTS: Collapsed across long HTWD and short HTWD, patellofemoral joint force and stress were greater in ball squat than wall squat at 30° ( P = 0.009), 40° ( P = 0.008), 90° ( P = 0.003), and 100° ( P = 0.005) knee angles during the squat descent, and greater in wall squat than ball squat at 100° ( P < 0.001), 90° ( P < 0.001), 80° ( P = 0.004), and 70° ( P = 0.009) knee angles during squat ascent. Collapsed across ball and wall squats, patellofemoral joint force and stress were greater with a short HTWD than a long HTWD at 100° ( P = 0.007) and 90° ( P = 0.008) knee angles during squat ascent. CONCLUSIONS: Patellofemoral joint loading changed according to both squat type and HTWD variations. These differences occurred in part due to differences in forces the wall or ball exerted on the trunk, including friction forces. Overall, patellofemoral force and stress were greater performing the bodyweight wall squat compared with the bodyweight ball squat. Moreover, squatting with short HTWD produced anterior knee displacement beyond the toes at higher knee angles, resulting in greater patellofemoral force and stress compared with squatting with long HTWD.

Patellofemoral Joint Loading in Forward Lunge With Step Length and Height Variations.

The objective was to assess how patellofemoral loads (joint force and stress) change while lunging with step length and step height variations. Sixteen participants performed a forward lunge using short and long steps at ground level and up to a 10-cm platform. Electromyography, ground reaction force, and 3D motion were captured, and patellofemoral loads were calculated as a function of knee angle. Repeated-measures 2-way analysis of variance (P < .05) was employed. Patellofemoral loads in the lead knee were greater with long step at the beginning of landing (10°-30° knee angle) and the end of pushoff (10°-40°) and greater with short step during the deep knee flexion portion of the lunge (50°-100°). Patellofemoral loads were greater at ground level than 10-cm platform during lunge descent (50°-100°) and lunge ascent (40°-70°). Patellofemoral loads generally increased as knee flexion increased and decreased as knee flexion decreased. To gradually increase patellofemoral loads, perform forward lunge in the following sequence: (1) minimal knee flexion (0°-30°), (2) moderate knee flexion (0°-60°), (3) long step and deep knee flexion (0°-100°) up to a 10-cm platform, and (4) long step and deep knee flexion (0°-100°) at ground level.

Patellofemoral Joint Loading During the Performance of the Forward and Side Lunge with Step Height Variations.

BACKGROUND: Forward and side lunge exercises strengthen hip and thigh musculature, enhance patellofemoral joint stability, and are commonly used during patellofemoral rehabilitation and training for sport. HYPOTHESIS/PURPOSE: The purpose was to quantify, via calculated estimates, patellofemoral force and stress between two lunge type variations (forward lunge versus side lunge) and between two step height variations (ground level versus 10 cm platform). The hypotheses were that patellofemoral force and stress would be greater at all knee angles performing the bodyweight side lunge compared to the bodyweight forward lunge, and greater when performing the forward and side lunge at ground level compared to up a 10cm platform. STUDY DESIGN: Controlled laboratory biomechanics repeated measures, counterbalanced design. METHODS: Sixteen participants performed a forward and side lunge at ground level and up a 10cm platform. Electromyographic, ground reaction force, and kinematic variables were collected and input into a biomechanical optimization model, and patellofemoral joint force and stress were calculated as a function of knee angle during the lunge descent and ascent and assessed with a repeated measures 2-way ANOVA (p<0.05). RESULTS: At 10° (p=0.003) knee angle (0° = full knee extension) during lunge descent and 10° and 30° (p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in forward lunge than side lunge. At 40°(p=0.005), 50°(p=0.002), 60°(p<0.001), 70°(p=0.006), 80°(p=0.005), 90°(p=0.002), and 100°(p<0.001) knee angles during lunge descent and 50°(p=0.002), 60°(p<0.001), 70°(p<0.001), 80°(p<0.001), and 90°(p<0.001) knee angles during lunge ascent patellofemoral joint force and stress were greater in side lunge than forward lunge. At 60°(p=0.009) knee angle during lunge descent and 40°(p=0.008), 50°(p=0.009), and 60°(p=0.007) knee angles during lunge ascent patellofemoral joint force and stress were greater lunging at ground level than up a 10cm platform. CONCLUSIONS: Patellofemoral joint loading changed according to lunge type, step height, and knee angle. Patellofemoral compressive force and stress were greater while lunging at ground level compared to lunging up to a 10 cm platform between 40° - 60° knee angles, and greater while performing the side lunge compared to the forward lunge between 40° - 100° knee angles. LEVEL OF EVIDENCE: II.

Shoulder External Rotational Properties During Physical Examination Are Associated With Injury That Requires Surgery and Shoulder Joint Loading During Baseball Pitching.

BACKGROUND: Throwing arm injuries are common because of the demand on the shoulder. The shoulder is qualitatively checked regularly by team physicians. Excessive instability and joint loading in baseball pitching are risk factors for throwing arm injuries. Knowledge of shoulder flexibility, range of motion, and joint loading may provide new insights for treatments to reduce the likelihood of injury incidence. PURPOSE: To investigate the relationship among injuries, shoulder external rotational properties, and shoulder joint loading in baseball pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: Pitching kinetics, shoulder rotational tests, and self-reported injury questionnaires were used to study 177 collegiate baseball pitchers. Pitching motion data were collected at 240 Hz using a motion capture system. A custom program calculated the shoulder joint loading. The shoulder rotational test quantitatively records shoulder range of motion and flexibility using a custom-made wireless device. Self-reported injury questionnaires were filled out during tests and yearly follow-ups. The total length of the study was 5 years. Analysis of variance, chi-square, and regression tests were performed to compare differences among groups and detect correlations with surgery and shoulder joint loadings. RESULTS: There were significant differences in shoulder flexibility among surgery groups. Shoulder external rotational properties during physical examination were significantly associated with shoulder joint loading in baseball pitching. High shoulder external rotation was associated with 14% to 36% lower shoulder posterior force and adduction, internal rotation, and horizontal adduction torque (P < .05). High shoulder flexibility was associated with 13% higher anterior force (P < .05). High shoulder external rotation before external rotation torque was applied was associated with 13% to 33% lower shoulder inferior force and adduction, internal rotation, and horizontal adduction torque (P < .05). There were no significant differences in shoulder joint loading among the surgery groups. CONCLUSION: Shoulder injuries that require surgery were associated with shoulder external rotation flexibility. High shoulder external rotation may be advantageous because it lowers the force and torque on the shoulder joint. CLINICAL RELEVANCE: The ability to understand shoulder external rotational properties, joint loading, and injury during baseball pitching helps further our understanding of injury mechanisms. The shoulder rotational test should be used as a screening tool to identify players at risk.

Detection of knee wobbling as a screen to identify athletes who may be at high risk for ACL injury.

This study developed a method to detect knee wobbling (KW) at low knee flexion. KW consists of quick uncontrollable medio-lateral knee movements without knee flexion, which may indicate a risk of ACL injury. Ten female athletes were recorded while performing slow, single-leg squats. Using motion capture data, the ratio of the frontal angular velocity to sagittal angular velocity (F/S) was calculated. An 'F/S spike' was defined when the F/S ratio exceeded 100%. The number of F/S spikes was counted before and after low-pass filtering at different cut-off frequencies. Intraclass correlation coefficients for KW and filtered F/S spike were analysed. KWs per squat cycle showed a median (range) of 3 (2-8) times. F/S spikes before and after low-pass filtering at 3-, 6-, 10-, and 15-Hz were 51 (12-108), 2 (0-6), 3 (1-12), 5 (2-21), and 9 (3-33) times, respectively. KWs and F/S spikes on motion capture with 6-Hz, low-pass filtering were well correlated (r = 0 .76). Median percentages of valgus and varus F/S spikes were 71% and 29%, respectively. After 6Hz, low-pass filtering, the number of F/S spikes was strongly correlated with observed KWs. An F/S spike assessment may be used to objectively detect KW, including flexion and varus/valgus angular velocity.

Sexual dimorphisms in three-dimensional masticatory muscle attachment morphometry regulates temporomandibular joint mechanics.

Temporomandibular joint (TMJ) disorders disproportionally affect females, with female to male prevalence varying from 3:1 to 8:1. Sexual dimorphisms in masticatory muscle attachment morphometry and association with craniofacial size, critical for understanding sex-differences in TMJ function, have not been reported. The objective of this study was to determine sex-specific differences in three-dimensional (3D) TMJ muscle attachment morphometry and craniofacial sizes and their impact on TMJ mechanics. Human cadaveric TMJ muscle attachment morphometry and craniofacial anthropometry (10Males; 11Females) were determined by previously developed 3D digitization and imaging-based methods. Sex-differences in muscle attachment morphometry and craniofacial anthropometry, and their correlation were determined, respectively using multivariate general linear and linear regression statistical models. Subject-specific musculoskeletal models of the mandible were developed to determine effects of sexual dimorphisms in mandibular size and TMJ muscle attachment morphometry on joint loading during static biting. There were significant sex-differences in craniofacial size (p = 0.024) and TMJ muscle attachment morphometry (p < 0.001). TMJ muscle attachment morphometry was significantly correlated with craniofacial size. TMJ contact forces estimated from biomechanical models were significantly, 23% on average (p < 0.001), greater for females compared to those for males when generating the same bite forces. There were significant linear correlations between TMJ contact force and both 3D mandibular length (R2 = 0.48, p < 0.001) and muscle force moment arm ratio (R2 = 0.68, p < 0.001). Sexual dimorphisms in masticatory muscle morphology and craniofacial sizes play critical roles in subject-specific TMJ biomechanics. Sex-specific differences in the TMJ mechanical environment should be further investigated concerning mechanical fatigue of TMJ discs associated with TMJ disorders.

Influence of graft type on sagittal plane knee biomechanics during stair ambulation following anterior cruciate ligament reconstruction.

BACKGROUND: Both graft type and surgical technique for anterior cruciate ligament reconstruction can affect knee biomechanics. Several studies reported the influence of graft type, but few have controlled the surgical technique and fully investigated stair ambulation. This study aimed to compare knee biomechanics during stair ambulation between patients treated with hamstring tendon graft and those treated with patellar tendon graft when anterior medial portal technique was used to drill femoral tunnel. METHODS: Two groups of patients (patellar tendon, n = 18; hamstring tendon, n = 18) at average 12 months after reconstruction surgery were recruited to ascend and descend a customized staircase in a gait lab. Joint kinematics and kinetics were calculated for both operated and contralateral intact limbs based on kinematic analysis and inverse dynamics. The influence of graft type on knee flexion angle and moment was identified using one-way mixed (graft type and limb side) analysis of variance with post-hoc paired t-test. FINDINGS: Significant interaction between graft and limb was found for knee flexion and range of motion. Only the hamstring tendon group had significant kinematic deficits on the operated limb than the contralateral limb during stair ascent and descent. No significant interaction was found for knee flexion moment. Both graft groups had significant deficits in peak knee flexion moment on the operated side during stair ascent and descent. INTERPRETATION: While the choice of graft type does not affect the restoration of knee dynamic loading, patellar tendon graft better restores knee flexion-extension kinematics during stair ambulation.

Three-dimensional temporomandibular joint muscle attachment morphometry and its impacts on musculoskeletal modeling.

In musculoskeletal models of the human temporomandibular joint (TMJ), muscles are typically represented by force vectors that connect approximate muscle origin and insertion centroids (centroid-to-centroid force vectors). This simplification assumes equivalent moment arms and muscle lengths for all fibers within a muscle even with complex geometry and may result in inaccurate estimations of muscle force and joint loading. The objectives of this study were to quantify the three-dimensional (3D) human TMJ muscle attachment morphometry and examine its impact on TMJ mechanics. 3D muscle attachment surfaces of temporalis, masseter, lateral pterygoid, and medial pterygoid muscles of human cadaveric heads were generated by co-registering measured attachment boundaries with underlying skull models created from cone-beam computerized tomography (CBCT) images. A bounding box technique was used to quantify 3D muscle attachment size, shape, location, and orientation. Musculoskeletal models of the mandible were then developed and validated to assess the impact of 3D muscle attachment morphometry on joint loading during jaw maximal open-close. The 3D morphometry revealed that muscle lengths and moment arms of temporalis and masseter muscles varied substantially among muscle fibers. The values calculated from the centroid-to-centroid model were significantly different from those calculated using the 'Distributed model', which considered crucial 3D muscle attachment morphometry. Consequently, joint loading was underestimated by more than 50% in the centroid-to-centroid model. Therefore, it is necessary to consider 3D muscle attachment morphometry, especially for muscles with broad attachments, in TMJ musculoskeletal models to precisely quantify the joint mechanical environment critical for understanding TMJ function and mechanobiology.

Biomechanical Evaluation of Two Arthroscopic Biceps Tenodesis Techniques: Proximal Interference Screw and Modified Percutaneous Intra-Articular Transtendon.

The percutaneous intra-articular transtendon (PITT) technique has recently been shown to have results comparable to those of more accepted techniques. Its mode of failure was secondary to the suture pulling through the tendon substance. A modification was made whereby the tendon is locked within the suture configuration in an attempt to avoid pullout. We compared this new technique with a well-accepted technique of all-arthroscopic interference screw. In each of 8 pairs of cadaveric shoulders (mean age, 55 years; range, 51-59 years), one shoulder was randomized to be treated with either modified PITT or interference screw (Biceptor; Smith & Nephew) biceps tenodesis, and the other shoulder was treated with the other technique. The tendons were preloaded at 10 N and then cycled at 0 to 50 N for 100 cycles at 1 Hz. Load to failure was calculated at a rate of 1.0 mm per second until peak load was observed. Mean (SD) ultimate load to failure was 157 (41) N for the modified PITT technique and 107 (29) N for the interference screw technique (P = .003). In 7 of 8 specimens, the interference screw technique failed at the junction of the tendon, the screw, and the bone interface. In 7 of 8 specimens, the PITT technique failed by the tendon slipping through the suture or pulling through transverse ligament/rotator interval tissue. Study results showed the modified PITT technique was a biomechanically superior construct.

Hierarchical classification of large-scale patient records for automatic treatment stratification.

In this paper, a hierarchical learning algorithm is developed for classifying large-scale patient records, e.g., categorizing large-scale patient records into large numbers of known patient categories (i.e., thousands of known patient categories) for automatic treatment stratification. Our hierarchical learning algorithm can leverage tree structure to train more discriminative max-margin classifiers for high-level nodes and control interlevel error propagation effectively. By ruling out unlikely groups of patient categories (i.e., irrelevant high-level nodes) at an early stage, our hierarchical approach can achieve log-linear computational complexity, which is very attractive for big data applications. Our experiments on one specific medical domain have demonstrated that our hierarchical approach can achieve very competitive results on both classification accuracy and computational efficiency as compared with other state-of-the-art techniques.

Knee moment and shear force are correlated with femoral tunnel orientation after single-bundle anterior cruciate ligament reconstruction.

BACKGROUND: Increasing evidence has shown that anatomic single-bundle anterior cruciate ligament reconstruction (ACLR) better restores normal knee kinematics and functionality than nonanatomic ACLR. Whether anatomic reconstruction results in better knee kinetics during daily activities has not been fully investigated. PURPOSE: To assess the relationship between femoral tunnel angle and kinetic parameters of the knee joint during walking after single-bundle ACLR and to compare the radiographic and kinetic results of patients who underwent anatomic ACLR with those of patients who underwent nonanatomic ACLR. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one patients who underwent unilateral ACLR were recruited, and 20 healthy subjects from a previous study were used as a control group. All surgical procedures were performed by a single surgeon, 11 using the transtibial (TT) technique and 10 using the anteromedial portal (AMP) technique. Femoral tunnel orientation was measured from posterior-to-anterior radiographs. Dynamic knee joint moments and shear forces during gait were evaluated using 3-dimensional motion analysis and inverse dynamics. Relationships between femoral tunnel angles and kinetic results were evaluated via linear regression. Results were compared between 2 ACLR groups and controls using 1-way analysis of variance. RESULTS: Femoral tunnel angle had significant correlations with peak external knee flexion moment and posterior shear force during early stance. The TT group had a significantly smaller (more vertical) mean femoral tunnel angle (19.4° ± 4.1°) than the AMP group (36.4° ± 5.8°). Significant reductions were found in the normalized peak external knee flexion moment (TT, 0.15 ± 0.12 Nm/kg·m; AMP, 0.25 ± 0.12 Nm/kg·m; control, 0.25 ± 0.16 Nm/kg·m) (P = .032) and posterior shear force (TT, 0.64 ± 0.55 N/kg; AMP, 1.10 ± 0.58 N/kg; control, 1.35 ± 0.55 N/kg) (P = .024) in the TT group compared with controls, but not in the AMP group. Moreover, a significantly greater medial shear force was found in the TT group during the late stance phase (TT, 1.08 ± 0.32 N/kg; AMP, 0.89 ± 0.26 N/kg; control, 0.83 ± 0.22 N/kg) (P = .038). A greater peak external knee adduction moment was found in both ACL groups during the early stance phase (TT, 0.25 ± 0.07 Nm/kg·m; AMP, 0.25 ± 0.07 Nm/kg·m; control, 0.19 ± 0.05 Nm/kg·m) (P < .01). CONCLUSION: Knee joint kinetic changes are seen within months (~10 months) after ACLR. This study revealed significant relationships between femoral tunnel orientation and postoperative knee joint flexion moment and posterior shear force during walking. The AMP technique provides better restoration of these knee kinetic parameters compared with the TT technique at this postoperative time point. CLINICAL RELEVANCE: The femoral tunnel angle measured from plain radiographs can be used as an important metric of postoperative knee joint kinetics. This information provides a better understanding of the knee joint's biomechanical environment after ACLR using commonly used single-bundle techniques.

Transtibial versus anteromedial portal technique in single-bundle anterior cruciate ligament reconstruction: outcomes of knee joint kinematics during walking.

BACKGROUND: In anterior cruciate ligament (ACL) reconstruction, the transtibial (TT) technique often creates a nonanatomically placed femoral tunnel, which is a frequent cause of surgical failure and postsurgical knee instability. Several studies reported that drilling the femoral tunnel through an anteromedial portal (AMP) yields a more anatomic tunnel position compared with the TT technique. PURPOSE: To compare the effectiveness of these two surgical techniques in restoring the intact knee joint kinematics during a physiological loading situation. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-four patients (TT, n = 12; AMP, n = 12; sex, weight, and height matched, and half with dominant leg involved) who underwent unilateral single-bundle ACL reconstruction by the same surgeon were recruited. Twenty healthy patients with no history of lower limb injuries were recruited as the control group. Tibiofemoral joint motion in 6 degrees of freedom (3 translations and 3 rotations) was determined during level walking by using a least mean square-based optimization algorithm. A redundant marker set was used to improve the accuracy of the motion analysis. Knee joint kinematics as well as spatiotemporal parameters were compared between these two techniques. RESULTS: The AMP technique restored the anterior-posterior translation of the knee joint, while the TT technique resulted in significantly greater (TT, 22.2 mm vs controls, 13.2 mm; P < .01) anterior femoral translations than in the healthy controls during the swing phase. Excessive femoral external (tibial internal) rotation (3.8°; P < .05) was found at midstance in the knees that were reconstructed using the TT technique; using the AMP technique, the external rotation offset was greatly reduced during the stance phase. However, knees repaired using the AMP technique were significantly less extended (5°; P < .05) compared with the knees of the controls during the late stance phase. Neither surgical technique restored the superior-inferior femoral translation to the intact level during the swing phase. CONCLUSION: The AMP technique better restores the anterior-posterior translation during the swing phase and femoral external rotation at midstance than the TT technique does. However, the AMP technique is also correlated with an extension loss during the late stance phase. CLINICAL RELEVANCE: The AMP femoral tunnel drilling technique can improve overall knee joint stability, but the increased difficulty with full extension may need to be considered.

Leveraging social supports for improving personal expertise on ACL reconstruction and rehabilitation.

In this paper, a social health support system is developed to assist both ACL (anterior cruciate ligament) patients and clinicians on making better decisions and choices for ACL reconstruction and rehabilitation. By providing a good platform to enable more effective sharing of personal expertise and ACL treatments, our social health support system can allow: (1) ACL patients to identify the best-matching social groups and locate the most suitable expertise for personal health management; and (2) clinicians to easily locate the best-matching ACL patients and learn from well-done treatments, so that they can make better decisions for new ACL patients (who have similar ACL injuries and close social principles with those best-matching ACL patients) and prescribe safer and more effective knee rehabilitation treatments.

Effect of lower limb dominance on knee joint kinematics after anterior cruciate ligament reconstruction.

BACKGROUND: Normal ambulatory kinematics of the knee joint is often not fully restored after anterior cruciate ligament reconstruction, which may increase the risk for cartilage degeneration and premature osteoarthritis in the involved knees. Lower limb dominance may have impacts on knee joint kinematics after anterior cruciate ligament reconstruction, which may lead to a different prevalence of cartilage degeneration. This study aimed to evaluate the knee joint kinematics among patients with reconstruction on the dominant and non-dominant side. METHODS: Forty-one subjects with unilateral anterior cruciate ligament reconstruction (19 dominant, 22 non-dominant) were recruited after being discharged from rehabilitation programs. Twenty healthy subjects were recruited as the control group. Six degrees-of-freedom tibiofemoral motion during level walking was determined using a redundant point cluster-based marker set. Tibiofemoral joint motion and its bilateral differences were compared within each group and between groups. FINDINGS: The non-dominant reconstructed knees had less extension compared to their contralateral knees at heel strike and during middle stance phase (P=0.02); whereas, the dominant reconstructed knees exhibited significantly reduced varus rotation (-2.1° on mean, P=0.027) and internal tibial rotation (P=0.034) compared to their contralateral knees during both stance and swing phases. INTERPRETATION: The results show that different kinematics has been developed between the involved dominant and non-dominant knees after anterior cruciate ligament reconstruction, especially the secondary rotations. The differences are consistent with the unequal prevalence of cartilage degeneration in the knee joint. The findings demonstrated that the lower limb dominance had a significant effect on post-surgery knee kinematics.

Three-dimensional joint kinematics of ACL-deficient and ACL-reconstructed knees during stair ascent and descent.

Mechanical environmental changes in the knee are induced by altered joint kinematics under cyclic loading during activities of daily living after anterior cruciate ligament (ACL) injury. This is considered a risk factor in progressive cartilage degeneration and the early onset of osteoarthritis following ACL injury and even after reconstructive surgery. The purpose of this study was to examine 3D joint kinematics of ACL-deficient and ACL-reconstructed knees to health controls during stair ascent and descent. A 3D optical video motion capture system was used to record coordinate data from reflective markers positioned on subjects as they ascended and descended a custom-built staircase. Spatiotemporal gait and knee joint kinematic variables were calculated and further analyzed. The ACL-deficient knees exhibited a significant extension deficit compared to the ACL-intact controls. A more varus and internally rotated tibial position was also identified in the ACL-deficient knees during both stair ascent and descent. The ACL-reconstructed knees exhibited less abnormality in both spatiotemporal gait parameters and joint kinematics, but these variables were not fully restored to a normal level. The kinematic profiles of the ACL-reconstructed knees were more similar to those of the ACL-deficient knees when compared to the ACL-intact knees. This suggests that the ACL-reconstructed knees had been "under-corrected" rather than "over-corrected" by the reconstructive surgery procedure. Findings from this study may provide more insight with respect to improving ACL reconstruction surgical techniques, which may aid the early progression of cartilage degeneration in ACL-reconstructed knees.

Cruciate ligament forces between short-step and long-step forward lunge.

PURPOSE: The purpose of this study was to compare cruciate ligament forces between the forward lunge with a short step (forward lunge short) and the forward lunge with a long step (forward lunge long). METHODS: Eighteen subjects used their 12-repetition maximum weight while performing the forward lunge short and long with and without a stride. EMG, force, and kinematic variables were input into a biomechanical model using optimization, and cruciate ligament forces were calculated as a function of knee angle. A two-factor repeated-measure ANOVA was used with a Bonferroni adjustment (P < 0.0025) to assess differences in cruciate forces between lunging techniques. RESULTS: Mean posterior cruciate ligament (PCL) forces (69-765 N range) were significantly greater (P < 0.001) in the forward lunge long compared with the forward lunge short between 0 degrees and 80 degrees knee flexion angles. Mean PCL forces (86-691 N range) were significantly greater (P < 0.001) without a stride compared with those with a stride between 0 degrees and 20 degrees knee flexion angles. Mean anterior cruciate ligament (ACL) forces were generated (0-50 N range between 0 degrees and 10 degrees knee flexion angles) only in the forward lunge short with stride. CONCLUSIONS: All lunge variations appear appropriate and safe during ACL rehabilitation because of minimal ACL loading. ACL loading occurred only in the forward lunge short with stride. Clinicians should be cautious in prescribing forward lunge exercises during early phases of PCL rehabilitation, especially at higher knee flexion angles and during the forward lunge long, which generated the highest PCL forces. Understanding how varying lunging techniques affect cruciate ligament loading may help clinicians prescribe lunging exercises in a safe manner during ACL and PCL rehabilitation.

Alterations in three-dimensional joint kinematics of anterior cruciate ligament-deficient and -reconstructed knees during walking.

BACKGROUND: High risk of cartilage degeneration and premature osteoarthritis development has been clinically observed in anterior cruciate ligament (ACL) deficient knees. The risk has not been significantly reduced even after ACL reconstructive surgery. It was hypothesized that three-dimensional knee joint kinematics has been altered after ACL injury, and the biomechanical alteration has not been fully restored to a normal level after reconstructive surgery. METHODS: Spatiotemporal parameters and three-dimensional knee joint rotations and translations were measured in ACL-deficient, ACL-reconstructed, and ACL-intact knees during level walking. The variables were compared between the ACL-deficient and ACL-intact knees, as well as between the ACL-reconstructed and ACL-intact knees. FINDINGS: Altered spatiotemporal variables and key event timings in a gait cycle were observed in both ACL-deficient and ACL-reconstructed subjects. Significant reduction of extension was observed in the ACL-deficient knees during midstance and in the ACL-reconstructed knees during swing phase. Greater varus and internal tibial rotation were identified in the ACL-deficient knees. Although being small in magnitude, these secondary kinematic alterations were consistent throughout the whole gait cycle, and such trends were not eliminated in the ACL-reconstructed knees. INTERPRETATION: Significant abnormalities of spatiotemporal performance and three-dimensional joint kinematics during walking were identified in the ACL-deficient knees. The ACL-reconstructed knees exhibited some improvement in joint kinematics, but not being fully restored to a normal level. Identification of biomechanical alterations during daily activities in ACL-deficient and ACL-reconstructed knees could help better understand clinical outcomes and seek improvement in surgical technique and rehabilitation regimen for ACL injury treatment.

Cruciate ligament tensile forces during the forward and side lunge.

BACKGROUND: Although weight bearing lunge exercises are frequently employed during anterior cruciate ligament and posterior cruciate ligament rehabilitation, cruciate ligament tensile forces are currently unknown while performing forward and side lunge exercises with and without a stride. METHODS: Eighteen subjects used their 12 repetition maximum weight while performing a forward lunge and side lunge with and without a stride. A motion analysis system and biomechanical model were used to estimate cruciate ligament forces during lunging as a function of 0-90 degrees knee angles. FINDINGS: Comparing the forward lunge to the side lunge across stride variations, mean posterior cruciate ligament forces ranged between 205 and 765N and were significantly greater (P<0.0025) in the forward lunge long at 40 degrees , 50 degrees , 60 degrees , 70 degrees , and 80 degrees knee angles of the descent phase and at 80 degrees , 70 degrees , 60 degrees knee angles of the ascent phase. There were no significant differences (P<0.0025) in mean posterior cruciate ligament forces between with and without stride differences across lunging variations. There were no anterior cruciate ligament forces quantified while performing forward and side lunge exercises. INTERPRETATION: Clinicians should be cautious in prescribing forward and side lunge exercises during early phases of posterior cruciate ligament rehabilitation due to relatively high posterior cruciate ligament forces that are generated, especially during the forward lunge at knee angles between 40 degrees and 90 degrees knee angles. Both the forward and side lunges appear appropriate during all phases of anterior cruciate ligament rehabilitation. Understanding how forward and side lunging affect cruciate ligament loading over varying knee angles may help clinicians better prescribe lunging exercises in a safe manner during anterior cruciate ligament and posterior cruciate ligament rehabilitation.