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Patient dissatisfaction following total knee replacement (TKR) procedures is likely influenced by both subjective and objective aspects. Increased pain and reduced performance on clinical tests have been shown in persons who are dissatisfied with the outcome of their surgery. However, it is unknown how overground walking kinematics and kinetics might differ in the dissatisfied versus satisfied patients following TKR surgery. This study compared the lower-extremity walking kinematics and kinetics of patients dissatisfied with their TKR to that of satisfied patients and healthy controls. Thirty nine subjects completed walking trials, including nine dissatisfied and 15 satisfied TKR patients and 15 healthy controls. A 2 × 3 repeated -measures analysis of variance was used to assess differences between groups and limbs (P

Contacting the base is a common injury mechanism for base runners in softball, with ankle sprains being the most common type of injury, but it is not known how the base affects lower extremity mechanics. The purpose of this study was to analyze lower extremity biomechanics while rounding a base. Sixteen recreationally active females with previous softball experience completed two base rounding conditions. A base was securely placed on the force place for the with base (WB) condition, and an outline of the base was taped on the force plate for the no base (NB) condition. Three-dimensional right-leg hip, knee, and ankle kinematics and kinetics were measured during the stance phase of the base rounding and analyzed using statistical parametric mapping (SPM). The WB condition resulted in decreased hip abduction ( p = 0.034), increased dorsiflexion ( p = 0.012), and decreased inversion ( p

In order to fully understand contact dynamics on a trampoline, a simulation approach using a musculoskeletal model coupled with a dynamic model of the trampoline is essential. The purpose of the study was to examine dynamics and selected lower extremity muscle forces in a landing and jumping movement on a trampoline, using a combination of finite element modeling and musculoskeletal modeling. The rigid frame of the trampoline was modeled in ADAMS and coupled with a finite element model of the elastic trampoline net surface in ANSYS. A musculoskeletal model of an elite trampoline athlete was further developed in LifeMod and combined with the finite element model of the trampoline. The results showed that the peak trampoline reaction forces (TRF) were 3400 N (6.6 BW) and 2900 N (5.6 BW) for the left and right limb, respectively. The right hip, knee and ankle joint reaction forces reached the maximum between 3000-4000 N (5.8 – 7.7 BW). The gluteus maximum and quadriceps reached the maximum muscle force of 380 N (0.7 BW) and 780 N (1.5 BW), respectively. Asymmetric loading patterns between left and right TRFs and lower extremities joint reaction forces were observed due to the need to generate the rotational movement during the takeoff. The observed rigid and erect body posture suggested that the hip and knee extensors played important roles in minimizing energy absorption and maximizing energy generation during the trampoline takeoff.

Highlights • Greater Q-Factor (QF) increased peak knee abduction moment in ergometer cycling. • For a given QF, peak knee abduction moment increased with increased workrate. • Increased QF did not affect peak knee extension moment. • Modulating frontal-plane joint loading via QF changes may have clinical applications., Background Q-Factor (QF), or the inter-pedal width, in cycling is similar to step-width in gait. Although increased step-width has been shown to reduce peak knee abduction moment (KAbM), no studies have examined the biomechanical effects of increased QF in cycling at different workrates in healthy participants. Methods A total of 16 healthy participants (8 males, 8 females, age: 22.4 ± 2.6 years, body mass index: 22.78 ± 1.43 kg/m2, mean ± SD) participated. A motion capture system and customized instrumented pedals were used to collect 3-dimensional kinematic (240 Hz) and pedal reaction force (PRF) (1200 Hz) data in 12 testing conditions: 4 QF conditions—Q1 (15.0 cm), Q2 (19.2 cm), Q3 (23.4 cm), and Q4 (27.6 cm)—under 3 workrate conditions—80 watts (W), 120 W, and 160 W. A 3 × 4 (QF × workrate) repeated measures of analysis of variance were performed to analyze differences among conditions (p < 0.05). Results Increased QF increased peak KAbM by 47%, 56%, and 56% from Q1 to Q4 at each respective workrate. Mediolateral PRF increased from Q1 to Q4 at each respective workrate. Frontal-plane knee angle and range of motion decreased with increased QF. No changes were observed for peak vertical PRF, knee extension moment, sagittal plane peak knee joint angles, or range of motion. Conclusion Increased QF increased peak KAbM, suggesting increased medial compartment loading of the knee. QF modulation may influence frontal-plane joint loading when using stationary cycling for exercise or rehabilitation purposes., Graphical abstract Image, graphical abstract

Background Osteoarthritis (OA) is a clinical problem affecting an estimated 27 million adults in the United States, with the only clear treatment options being pain management. Cycling is an integral component of exercise for individuals with knee osteoarthritis, while the joint reaction forces during cycling remain unknown. Methods Thirteen subjects with medial compartment knee osteoarthritis and eleven healthy subjects performed a cycling protocol with a neutral pedal and four pedal modifications. Six hundred muscle-actuated inverse-dynamic simulations (24 subjects, 5 trials in each of 5 conditions) were performed to estimate joint reaction force differences between conditions. Findings Subjects with knee osteoarthritis had many significant changes among them was a reduction in knee adduction-abduction moment by 45% (5° lateral wedge), 77% (10° lateral wedge), 54% (5° toe-in) and 58% (10° toe-in). Conversely the healthy subjects had no significant changes in the knee adduction-abduction moment for the lateral wedge conditions and the 5° toe-in but did decrease by 18% for the 10° toe-in condition. When comparing the cohorts across the different pedal conditions, the data showed many significant differences among the groups. Interpretation This study showed that while cycling in different pedal modifications, the knee osteoarthritis subjects had more beneficial changes in their knee adduction-abduction moment compared to the healthy subjects with the lateral-wedge modification resulting in the greatest impact on the subjects with knee osteoarthritis. Both groups had greater contact forces at the hip and ankle across pedal modifications compared to neutral. For the knee, subjects with osteoarthritis mostly decreased their knee contact forces but the healthy subjects mostly increased these forces with all pedal modifications.

Changes in the workrate and seat position have been linked to changes in internal knee extension moment. However, there is limited research on effects of those changes on knee kinetics in recumbent bike. The purpose of this study was to examine the effects of different seat positions and workrates on KAbM, knee extension moment and perceived effort during stationary recumbent cycling. Fifteen cyclists cycled on a recumbent ergometer in 6 test conditions of pedalling in far, medium and close seat positions in each of the two workrates of 60 and 100 W at the cadence of 80 RPM. A three-dimensional motion analysis system and a pair of instrumented pedals collected kinematic and kinetic data. A 3 ×2 repeated measures ANOVA was used to examine the effect of seat positions and workrates on selected variables of interest. Different seat positions did not change either peak KAbM (p = 0.592) or knee extension moment (p = 0.132). Increased workrates significantly increased peak KAbM (p

The aim of this study was to examine ground reaction force (GRF) and knee biomechanical characteristics of certain knee-unfriendly Tai Chi movement elements, comparing them with slow walking, and e...

The purpose of this study was to determine how tibiofemoral joint compressive forces and knee joint-spanning muscle forces during uphill walking change compared to level walking in patients with total knee arthroplasty (TKA). A musculoskeletal model capable of resolving total (TCF), medial (MCF), and lateral (LCF) tibiofemoral compressive forces was used to determine compressive forces and muscle forces during level and uphill walking on a 10 deg incline for twenty-five post-TKA patients. A 2 × 2 (slope: level and 10 deg × limb: replaced and nonreplaced) repeated measures analysis of variance was used to detect differences in knee contact forces between slope and limb conditions and their interaction. Peak loading-response TCF, MCF, and LCF were greater during uphill walking than level walking for nonreplaced limbs. During uphill walking, peak loading-response TCF was smaller in replaced limbs compared to nonreplaced limbs with no change in MCF or LCF. Peak knee extension moment and knee extensor muscle force were smaller in replaced limbs compared to nonreplaced limbs during uphill walking. During level walking, replaced and nonreplaced limbs experienced rather equal joint loading; however, replaced limb experienced reduced joint loading during uphill walking. Differences in joint loading between replaced and nonreplaced limbs were not present during level walking, suggesting compensation from the replaced limb during the more difficult task. Uphill walking following TKA promotes more balanced loading of replaced limbs during stance; however, these benefits may come at the expense of increased loading on nonreplaced limbs.

Introduction Cycling is a common modality for rehabilitation and exercise. However, there is a lack of information in the literature on the effects of saddle height adjustments on internal peak knee abduction moment, which is an important loading variable for the medial compartment of tibiofemoral joint for patients with knee osteoarthritis. The purpose of this study was to examine effects of saddle height on frontal-plane biomechanics of the knee during cycling. Methods Fourteen recreational cyclists (age: 57.1 ± 6.37 years) performed 2-min bouts of cycling at three saddle heights of 40°, 30° and 20° knee extension angle at bottom crank position, at two workrates of 80 and 120 W. Three-dimensional kinematic, kinetic, and electromyography data were collected and analyzed using a 3 × 2 (height × workrate) analysis of variance (ANOVA). Results There were no changes in internal knee abduction moment across saddle heights. Increases in saddle height from 40° to both 30° and 20° reduced the knee extension moment (d = 0.3 and 0.4, respectively, P = 0.012). Increases in workrate increased both knee abduction and extension moments (η2p = 0.75 and 0.88, respectively, P Conclusions Increased knee extension moment with decreased saddle height is likely to indicate increased knee joint load.

Stationary cycling is typically recommended following total knee arthroplasty (TKA) operations. However, knee joint biomechanics during cycling remains mostly unknown for TKA patients. Biomechanical differences between the replaced and non-replaced limb may inform applications of cycling in TKA rehabilitation. The purpose of this study was to examine the knee joint biomechanics of TKA patients during stationary cycling. Fifteen TKA participants cycled at 80 revolutions per minute and workrates of 80 W and 100 W while kinematics (240 Hz) and pedal reaction forces using a pair of instrumented pedals (1200 Hz) were collected. A 2x2 (limb × workrate) repeated measures ANOVA was run with an alpha of 0.05. Peak knee extension moment (KEM, p = 0.034) and vertical pedal reaction force (p = 0.038) were significantly reduced in the replaced limbs compared to non-replaced limbs by 21.3% and 5.3%, respectively. Peak KEM did not change for TKA patients with the increased workrate (p = 0.750). However, both peak hip extension moment (p = 0.009) and ankle plantarflexion moment (p = 0.017) increased due to increased workrate. Patients following TKA showed similar decreases in peak KEM and vertical pedal reaction force in their replaced compared to non-replaced limbs, as previously seen in gait. Patients of TKA may rely on their hip and ankle extensors to increases in workrate. Increasing intensity by 20 W did not exacerbate any inter-limb differences for peak KEM and vertical PRF.

Background The purpose of this study was to compare knee biomechanics of the replaced limb to the non-replaced limb of total knee replacement (TKR) patients and healthy controls during walking on level ground and on decline surfaces of 5°, 10°, and 15°. Methods Twenty-five TKR patients and 10 healthy controls performed 5 walking trials on different decline slopes on a force platform and an instrumented ramp system. Two analyses of variance, 2 × 2 (limb × group) and 2 × 4 (limb × decline slope), were used to examine selected biomechanics variables. Results The replaced limb of TKR patients had lower peak loading-response and push-off knee extension moment than the non-replaced and the matched limb of healthy controls. No differences were found in loading-response and push-off knee internal abduction moments among replaced, non-replaced, and matched limb of healthy controls. The knee flexion range of motion, peak loading-response vertical ground reaction force, and peak knee extension moment increased across all slope comparisons between 0° and 15° in both the replaced and non-replaced limb of TKR patients. Conclusion Downhill walking may not be appropriate to include in early stage rehabilitation exercise protocols for TKR patients.

Background Increased peak external knee adduction moments exist for individuals with knee osteoarthritis and varus knee alignments, compared to healthy and neutrally aligned counterparts. Walking with increased toe-in or increased step width have been individually utilized to successfully reduce 1st and 2nd peak knee adduction moments, respectfully, but have not previously been combined or tested among all alignment groups. The purpose of this study was to compare toe-in only and toe-in with wider step width gait modifications in individuals with neutral, valgus, and varus alignments. Methods Thirty-eight healthy participants with confirmed varus, neutral, or valgus frontal-plane knee alignment through anteroposterior radiographs, performed level walking in normal, toe-in, and toe-in with wider step width gaits. A 3 × 3 (group × intervention) mixed model repeated measures ANOVA compared alignment groups and gait interventions (p Results The 1st peak knee adduction moment was reduced in both toe-in and toe-in with wider step width compared to normal gait. The 2nd peak adduction moment was increased in toe-in compared to normal and toe-in with wider step width. The adduction impulse was also reduced in toe-in and toe-in with wider step width compared to normal gait. Peak knee flexion and external rotation moments were increased in toe-in and toe-in with wider step width compared to normal gait. Conclusion Although the toe-in with wider step width gait seems to be a viable option to reduce peak adduction moments for varus alignments, sagittal, and transverse knee loadings should be monitored when implementing this gait modification strategy.

Many unilateral total knee replacement (TKR) patients will need a contralateral TKR. Differences in knee joint biomechanics between bilateral patients and unilateral patients are not well established. The purpose of this study was to examine knee joint differences in level walking between bilateral and unilateral patients, and asymptomatic controls, using principal component analysis. Knee joints of 1st replaced limbs of 15 bilateral patients (69.40 ± 5.04 years), 15 replaced limbs of unilateral patients (66.47 ± 6.15 years), and 15 asymptomatic controls (63.53 ± 9.50 years) were analyzed during level walking. Principal component analysis examined knee joint sagittal- and frontal-plane kinematics and moments, and vertical ground reaction force (GRF). A one-way analysis of variance analyzed differences between principal component scores of each group. TKR patients exhibited more flexed and abducted knees throughout stance, decreased sagittal knee range of motion (ROM), increased early-stance adduction ROM, decreased loading-response knee extension and push-off knee flexion moments, decreased loading-response and push-off peak knee abduction moment (KAbM), increased KAbM at midstance, increased midstance vertical GRF, and decreased loading-response and push-off vertical GRF. Additionally, bilateral patients exhibited reduced sagittal knee ROM, increased adduction ROM, decreased sagittal knee moments throughout stance, decreased KAbM throughout stance, an earlier loading-response peak vertical GRF, and a decreased push-off vertical GRF, compared to unilateral patients. TKR patients, especially bilateral patients had stiff knee motion in the sagittal-plane, increased frontal-plane joint laxity, and a quadriceps avoidance gait.

As Q-Factor (QF: inter-pedal distance) is increased, the internal knee abduction moment (KAbM) also increases, however it is unknown if this increased KAbM is associated with increased medial compartment knee joint contact force in cycling. In the absence of in vivo measurement, musculoskeletal modeling simulations may provide a viable option for estimating knee joint contact forces in cycling. The primary purpose of this study was to investigate the effect of increasing QF on knee joint total (TCF), and medial (MCF) compartment contact force during ergometer cycling. The secondary purpose was to evaluate whether KAbM and knee extension moment are accurate predictors of MCF in cycling. Musculoskeletal simulations were performed to estimate TCF and MCF for sixteen participants cycling at an original QF (150 mm), and wide QF (276 mm), at 80 W and 80 rotations per minute. Paired samples t-tests were used to detect differences between QF conditions. MCF increased significantly, however, TCF did not change at wide QF. Peak knee extensor muscle force did not change at wide QF. Peak knee flexor muscle force was significantly reduced with wide QF. Regression analyses showed KAbM and knee extension moments explained 87.4% of the variance in MCF when considered alongside QF. The increase of MCF may be attributed to increased frontal-plane pedal reaction force moment arm. Future research may seek to implement QF modulation as a part of rehabilitation or training procedures utilizing cycling in cases where medial compartment joint loading is of importance.

This study compared biomechanics during stair ascent in replaced and non-replaced limbs of total knee arthroplasty (TKA) patients with control limbs of healthy participants. Thirteen TKA patients and fifteen controls performed stair ascent. Replaced and non-replaced knees of TKA patients were less flexed at contact compared to controls. The loading response peak knee extension moment was greater in control and non-replaced knees compared with replaced. The push-off peak knee abduction moment was elevated in replaced limbs compared to controls. Loading and push-off peak hip abduction moments were greater in replaced limbs compared to controls. The push-off peak hip abduction moment was greater in non-replaced limbs compared to controls. Future rehabilitation protocols should consider the replaced knee and also the non-replaced knee and surrounding joints.

Total knee replacement patients have shown reductions in knee flexion range of motion, knee extensor moments, and gait speed during stair ascent and stair descent. However, it is unknown how patients dissatisfied with their total knee replacement differ from those who are satisfied during more difficult activities such as stair negotiation. Therefore, the purpose of this study was to compare knee biomechanics of patients who are dissatisfied with their joint replacement to those who are satisfied and healthy participants during stair negotiation.Nine dissatisfied, fifteen satisfied patients and fifteen healthy participants participated, completing stair ascent and descent trials on an instrumented staircase. A 2 × 3 ANOVA was used to analyze biomechanical differences between groups and limbs during both activities.The dissatisfied group showed reduced 2nd peak vertical GRF (P ≤ 0.0040) and loading-response knee extension moments (P ≤ 0.0041) in their operated limb compared to their non-operated limb and to satisfied and healthy groups during stair ascent. First peak vertical GRF (P 0.0088) and both loading-response (P 0.0117) and push-off abduction moments (P 0.0028) showed reduced values in operated limbs compared to non-operated limbs for all groups. During stair descent, the dissatisfied group showed reduced loading-response and push-off knee extension moments (P ≤ 0.006) in their operated limb compared to their non-operated limb and the healthy group. The loading-response knee extension (P 0.0379) and abduction moments (P ≤ 0.0048) were also reduced in the dissatisfied group compared to the satisfied group.Patients who were dissatisfied showed asymmetrical loading of the knees in conjunction, which may have contributed to their dissatisfaction.

The purpose of this study was to investigate knee biomechanics in uphill walking on slopes of 5°, 10° and 15° for total knee replacement (TKR) patients. Twenty-five post-TKR patients and ten healthy controls performed five walking trials on level ground and different slopes on an instrumented ramp system. A 2 × 2 × 4 (limb × group × incline slope) mixed model ANOVA was used to examine selected variables. The peak knee extension moment (KEM) was greater in 15° uphill walking compared to level, 5° and 10° uphill walking. TKR patients had lower peak KEM and smaller knee extension range of motion than healthy controls in all walking conditions. The Replaced Limb showed lower peak KEM in 10° and 15° uphill walking than the Non-replaced Limb and smaller knee extension range of motion (ROM) in 10° uphill walking. Knee extension and abduction ROM increased with increased incline angles. The greater peak loading-response vertical ground reaction force was found in level walking compared to three levels of uphill walking. The peak loading-response knee abduction moment was greater in level walking compared to 10° and 15° uphill walking. However, the medial knee contact force was greater in non-replaced limb compared to replaced limb in 10° and 15° uphill walking. The results suggest 5° uphill walking may have the potential to become a safe exercise for unilateral TKR patients.

Iliotibial band syndrome (ITBS) is a common overuse knee injury that is twice as likely to afflict women compared to men. Lower extremity and trunk biomechanics during running, as well as hip abductor strength and iliotibial band flexibility, are factors believed to be associated with ITBS. The purpose of this cross-sectional study was to determine if differences in lower extremity and trunk biomechanics during running exist among runners with current ITBS, previous ITBS, and controls. Additionally, we sought to determine if isometric hip abductor strength and iliotibial band flexibility were different among groups. Twenty-seven female runners participated in the study. Participants were divided into three equal groups: current ITBS, previous ITBS, and controls. Overground running trials, isometric hip abductor strength, and iliotibial band flexibility were recorded for all participants. Discrete joint and segment biomechanics, as well as hip strength and flexibility measures were analyzed using a one-way analysis of variance. Runners with current ITBS exhibited 1.8 (1.5)° greater trunk ipsilateral flexion and 7 (6)° less iliotibial band flexibility compared to runners with previous ITBS and controls. Runners with previous ITBS exhibited 2.2 (2.9) ° less hip adduction compared to runners with current ITBS and controls. Hip abductor strength 3.3 (2.6) %BM×h was less in runners with previous ITBS but not current ITBS compared to controls. Runners with current ITBS may lean their trunk more towards the stance limb which may be associated with decreased iliotibial band flexibility.

Static frontal plane tibiofemoral alignment is an important factor in dynamic knee alignment and knee adduction moments. However, little is known about the relationship between alignment and compartment contact forces or muscle control strategies. The purpose of this study was to estimate medial (MCF) and lateral (LCF) compartment knee joint contact forces and muscle forces during stair ascent using a musculoskeletal model implementing subject specific knee alignments. Kinematic and kinetic data from 20 healthy individuals with radiographically confirmed varus or valgus knee alignments were simulated using alignment specific models to predict MCFs and LCFs. Muscle forces were determined using static optimization. Independent samples t-tests compared contact and knee and frontal plane hip muscle forces between groups during weight acceptance and during pushoff. The varus group exhibited increased weight acceptance peak MCFs, while the valgus group exhibited increased pushoff peak LCFs. The varus group utilized increased vasti muscle forces during weight acceptance and hip adductor forces during pushoff. The valgus group utilized increased hip abductor forces during pushoff. The alignment dependent contact forces provide evidence of the significance of frontal plane knee alignment in healthy individuals, which may be important in considering future knee joint health. The differing muscle control strategies between alignments detail specific neuromuscular responses to control frontal plane knee loads.

Purpose An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moments (KAbM). Increases in step width (SW) may act to reduce this moment. The purpose of this study was to determine the effects of increased SW on knee biomechanics during stair negotiation of healthy-weight and obese participants. Methods Participants (24: 10 obese and 14 healthy-weight) used stairs and walked over level ground while walking at their preferred speed in two different SW conditions – preferred and wide (200% preferred). A 2 × 2 (group × condition) mixed model analysis of variance was performed to analyze differences between groups and conditions (p Results Increased SW increased the loading-response peak knee extension moment during descent and level gait, decreased loading-response KAbMs, knee extension and abduction range of motion (ROM) during ascent, and knee adduction ROM during descent. Increased SW increased loading-response peak mediolateral ground reaction force (GRF), increased peak knee abduction angle during ascent, and decreased peak knee adduction angle during descent and level gait. Obese participants experienced disproportionate changes in loading-response mediolateral GRF, KAbM and peak adduction angle during level walking, and peak knee abduction angle and ROM during ascent. Conclusion Increased SW successfully decreased loading-response peak KAbM. Implications of this finding are that increased SW may decrease medial compartment knee joint loading, decreasing pain and reducing joint deterioration. Increased SW influenced obese and healthy-weight participants differently and should be investigated further.

The purpose of this review was to summarize the biomechanical adaptations during stair ambulation that occur after total knee arthroplasty (TKA). Articles were identified by searching PubMed and Web of Science. During stair ascent, knee flexion angle at heel strike and walking velocity were reduced in TKA subjects compared to controls. Results of other variables were not consistent between studies. During stair descent only one study found any differences for knee moments in the sagittal and frontal plane between TKA subjects and controls. Other results during stair descent were not consistent between studies. Differences in methods can partially explain discrepancies between studies in this review. More studies with consistent and improved methods are needed in order to provide better understanding of stair ambulation following TKA.

article i nfo Background: Peak internal knee abduction moment is a common surrogate variable associated with medial compartment knee loading. Stair descent has been shown to yield a greater peak knee abduction moment compared to level-walking. Changes in step width (SW) may lead to changes in frontal plane lower extrem- ity limb alignment in the frontal plane and alter peak knee abduction moment. The purpose of this study was to investigate the effects of increased SW on frontal plane knee biomechanics during stair descent in healthy older adults. Methods: Twenty healthy adults were recruited for the study. A motion analysis system was used to obtain three-dimensional lower limb kinematics during testing. An instrumented 3-step staircase with two additional customized wooden steps was used to collect ground reaction forces (GRF) data during stair de- scent trials. Participants performed five stair descent trials at their self-selected speed using preferred, wide (26% leg length), and wider (39% leg length) SW. Results: The preferred normalized SW in older adults during stair descent was 20% of leg length. Wide and wider SW during stair descent reduced both first and second peak knee adduction angles and abduction moments compared to preferred SW in healthy adults. Conclusions: Increased SW reduced peak knee adduction angles and abduction moments. The reductions in knee abduction moments may have implications in reducing medial compartment knee loads during stair descent.

The purpose of the study was to establish a dynamics model and a three-dimensional (3D) finite element model to analyze loading characteristics of femoral neck during walking, squat, single-leg standing, and forward and lateral lunges. One male volunteer performed three trials of the five movements. The 3D kinematic data were captured and imported into the LifeMOD to establish a musculoskeletal dynamics model to obtain joint reaction and muscle forces of iliacus, gluteus medius, gluteus maximus, psoas major and adductor magnus. The loading data LfeMOD were imported and transformed into a hip finite-element model. The results of the finite element femur model showed that stress was localized along the compression arc and the tension arc. In addition, the trabecular bone and tension lines of the Ward's triangle also demonstrated high stress. The compact bone received the greatest peak stress in the forward lunge and the least stress in the squat. However, the spongy bone in the femoral neck region had the greatest stress during the walk and the least stress in the squat. The results from this study indicate that the forward lunge may be an effective method to prevent femoral neck fractures. Walking is another effective and simple method that may improve bone mass of the Ward's triangle and prevent osteoporosis and femoral neck fracture.

Background Physical activity is recommended for older adults, including those with knee pathology. However, demands on the knee during popular recreational activities are unclear. The study purpose was to determine knee biomechanics in healthy older men during golf and bowling and compare them to activities of daily living. Methods Three-dimensional motion analysis was used to determine knee biomechanics in 19 healthy males (45–73 years): 11 golfers and eight bowlers. Subjects performed walking, stair ascent, stair descent, and either golf or bowling. Comparisons were made between the recreational activity and activities of daily living. Results During bowling, flexion angle at peak extensor moment was as high as during stair descent, and peak extensor moment was as high as during stair ascent. For the golf lead knee, flexion angle at peak extensor moment and peak extensor moment were as high as during stair ascent, and peak abduction moment, internal and external rotation angles were larger than during all activities of daily living. Peak external rotation angle for the golf trail knee was larger than all activities of daily living. Conclusion The greatest challenge for the knee of healthy older males during bowling is eccentric control of knee flexion. Golf poses challenges in all three planes of motion for the lead knee and in the transverse plane for the trail knee. Clinical relevance Comparing mechanical demands on the knee during bowling and golf to those of stair negotiation provides a reference for clinicians when recommending recreational activities for older adults with knee pathology.

Objective—To use an inverse dynamics method to describe the motion of the canine pelvic limb in 3 dimensions. Animals—6 healthy adult dogs. Procedures—For each dog, 16 anatomic and tracking markers were used to define the center of rotation for the pelvic limb joints and a kinematic model was created to describe the motion of the pelvic limb. Kinetic, kinematic, and morphometric data were combined so that an inverse dynamics method could be used to define angular displacement, joint moment, and power of the hip, stifle, and tibiotarsal (hock) joints in the sagittal, frontal, and transverse planes. Results—Movement and energy patterns were described for the hip, stifle, and hock joints in the sagittal, frontal, and transverse planes. Conclusions and Clinical Relevance—Knowledge of the 3-D movement of the pelvic limb can be used to better understand its motion, moment, and energy patterns in healthy dogs and provide a referent with which gaits of dogs with pelvic limb injuries before and after surgical repair or rehabilitation can be compared and characterized. This information can then be used to guide decisions regarding treatment options for dogs with pelvic limb injuries.

BackgroundNo studies have compared effectiveness of resistance training and Tai Ji exercise on relieving symptoms of knee osteoarthritis (OA). The purpose of the study was to evaluate effects of a 10-week Tai Ji and resistance training intervention on improving OA symptoms and mobility in seniors with knee OA.MethodsThirty-one seniors (60–85 years) were randomly assigned to a Tai Ji program (n = 12), a resistance training program (n = 13), and a control group (n = 6). All participants completed the Western Ontario and McMaster (WOMAC) Osteoarthritis Index and performed three physical performance tests (6-min walk, timed-up-and-go, and timed stair climb and descent) before and after the 10-week intervention.ResultsThe participants in the resistance training group significantly improved on the timed-up-and-go test (p = 0.001), the WOMAC pain sub-score (p = 0.006), WOMAC stiffness sub-score (p < 0.001), and WOMAC physical function sub-score (p = 0.011). The Tai Ji group significantly improved on the timed-up-and-go test (p < 0.001), but not on the WOMAC scores.ConclusionResistance training was effective for improving mobility and improving the symptoms of knee OA. Tai Ji was also effective for improving mobility, but did not improve knee OA symptoms.

The purpose of this study was to investigate the differences of knee concentric and eccentric strength and impact related knee biomechanics between jumpers and non-jumpers during step-off landing tasks. Ten male college swimming athletes (non-jumpers) and 10 track and volleyball athletes (jumpers) were recruited to participate in two test sessions: a muscle strength testing session of concentric and eccentric extension for dominant knee joint at 60°/s and 180°/s and a landing testing session. The participants performed five trials of step-off landing in each of four conditions: soft and stiff landing from 0.4m and 0.6m landing heights. The three-dimensional kinematics and ground reaction force were recorded simultaneously during step-off landing conditions. The results showed that the jumpers had significantly greater peak knee eccentric extension and concentric flexion torques compared to the non-jumpers. No significant group effects were found for peak vertical ground reaction force and knee range of motion during landing. The jumpers had significantly greater knee contact flexion angle, maximum knee flexion angle and initial knee extension moment compared to the non-jumpers. These results suggest that these athletes adopted a favorable impact attenuation strategy that is related to the greater knee eccentric muscle strength and training.

Barefoot or minimal footwear running is currently a highly debated topic among runners and researchers. Several footwear companies have developed minimal running footwear to simulate barefoot running but few studies have compared minimal footwear to barefoot and shoes during running. The primary goal of this study was to compare acute changes in three-dimensional (3D) ground reaction forces (GRFs) and lower limb kinematics and kinetics of habitually shod rearfoot strike (RFS) and forefoot strike (FFS) runners between minimal shoes (MSH), barefoot and neutral cushion running shoes (SH). Lower extremity joint biomechanical variables of RFS and FFS runners were analysed using a 3D motion capture system and a force platform during overground running in barefoot, MSH and running shoes. Barefoot and MSH showed a more anterior foot strike than shoes. The loading rate of the impact peak GRF was greater in barefoot and MSH than in shoes. MSH showed greater ankle plantarflexor moment and negative power in early sta...

Biomechanical data for gait in unstable rocker bottom shoes reported in the literature is not comprehensive across available shoe types. Purpose: The objective of this study was to comprehensively evaluate centre of pressure (COP), ground reaction force (GRF), joint kinematics and kinetics, and electromyography (EMG) of selected muscles while walking in an unstable shoe compared to a control shoe. Methods: Fifteen subjects performed five walking trials at 1.3 m/s and 1.8 m/s in control and unstable shoes. Kinematic, GRF and EMG data were simultaneously collected. Results: The unstable shoe caused an increased mediolateral COP displacement. Greater loading rate of initial peak vertical GRF, reduced ankle plantarflexion range of motion (ROM) and greater total sagittal-plane ankle ROM were also observed for the unstable shoe compared to the control shoe. Peak dorsiflexion and plantarflexion moments, peak knee flexion moment as well as EMG activation of tibialis anterior and rectus femoris were reduced in the...

Knee injuries are highly prevalent in athletic populations, particularly among female athletes. Many of these injuries occur during landing from a jump. Various comprehensive knee injury prevention programs have been developed to date. However, there is a need to determine which components of these programs contribute directly to changes in knee biomechanics. Therefore, the purpose of this study was to investigate the immediate effect of three different simple verbal instructions on knee biomechanics during landing in adult female recreational athletes. Three-dimensional kinematic and kinetic analysis of landing from a countermovement jump was conducted in a counterbalanced cross-over repeated measures design. Results indicated that the instruction to land with equal weight distribution reduced the asymmetry of peak vertical ground reaction force compared to the control condition. The instruction to land softly reduced peak vertical ground reaction force and increased peak knee flexion compared to the control condition. The instruction to land with knees over toes increased peak knee flexion compared to the control condition. These findings indicate that verbal instruction may be a key component of the effects seen in previous research studies that have investigated the benefits of more complex training programs designed to reduce knee injury risk in female athletes.

Background Short-leg walking boots are a common intervention for acute and chronic lower extremity injury. Few studies have examined the neuromuscular adaptations associated with short-leg walking boots and no previous study has investigated timing characteristics of muscle activation during gait. The purpose of the current study was to examine the timing and amplitudes of muscle activation of the extrinsic ankle musculature during walking in two types of short-leg walking boots. Methods Eleven healthy young adults performed five level walking trials at a self-selected pace in each of three conditions: normal walking, Gait Walker and Equalizer short-leg walking boots. Ground reaction forces were collected from a force platform while surface electromyography (EMG) was collected from the tibialis anterior, peroneus longus and medial gastrocnemius. EMG signals were rectified and smoothed using the root mean squared with a 20-ms smoothing window and were normalized to the largest mean of the normal walking trials. A repeated measures analysis of variance was used to assess the effect of short-leg walking boots on the onset, duration and amplitude of muscle activation. Results Short-leg walking boots were generally associated with earlier onsets of muscle activation and longer durations of muscle activation. However, there was no reduction in EMG amplitude. Conclusion The findings of this study show that the induced alterations in muscle activation patterns may limit the short-leg walking boots.

OBJECTIVE: To investigate biomechanical (kinematic) differences between 2 ankle brace testing protocols: landing on an inverted surface (IS) and inversion drop on an inversion platform. DESIGN: Five trials in each of 4 dynamic movement conditions were performed: inversion drop and drop landing from 0.45 m onto an IS without and with an ankle brace. A 7-camera motion analysis system was used to obtain the 3-dimensional kinematics. A 2 × 2 (brace × movement) repeated measures analysis of variance was used to evaluate selected variables for inversion drop and IS landing. SETTING: Research laboratory. PATIENTS: Eleven healthy subjects participated in the study. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Maximum ankle frontal plane and sagittal plane joint angles, range of motion, and maximum angular velocity. RESULTS: The IS landing resulted in significantly earlier maximum inversion, inversion velocities, dorsiflexion range of motion (ROM), contact dorsiflexion velocity, and maximum dorsiflexion velocity compared with the inversion drop. The ankle brace application during the IS landing reduced the contact plantarflexion angle, dorsiflexion ROM and maximum dorsiflexion velocity, and maximum inversion. CONCLUSIONS: The results from this study showed that the IS landing protocol produced significantly earlier maximum inversion angle and velocity and inversion velocities compared with the inversion drop protocol. These results showed that the IS landing is more demanding and should be considered in future investigations of ankle braces and lateral ankle performance/injury mechanisms.

Controlled laboratory study.To examine effectiveness of an ankle brace with a subtalar locking system in restricting ankle inversion during passive and dynamic movements.Semirigid ankle braces are considered more effective in restricting ankle inversion than other types of brace, but a semirigid brace with a subtalar locking system may be even more effective.Nineteen healthy subjects with no history of major lower extremity injuries were included in the study. Participants performed 5 trials of an ankle inversion drop test and a lateral-cutting movement without wearing a brace and while wearing either the Element (with the subtalar locking system), a Functional ankle brace, or an ASO ankle brace. A 2-way repeated-measures analysis of variance (ANOVA) was used to assess brace differences (P?.05).All 3 braces significantly reduced total passive ankle frontal plane range of motion (ROM), with the Element ankle brace being the most effective. For the inversion drop the results showed significant reductions in peak ankle inversion angle and inversion ROM for all 3 braces compared to the no brace condition; and the peak inversion velocity was also reduced for the Element brace and the Functional brace. In the lateral-cutting movement, a small but significant reduction of the peak inversion angle in early foot contact and the peak eversion velocity at push-off were seen when wearing the Element and the Functional ankle braces compared to the no brace condition. Peak vertical ground reaction force was reduced for the Element brace compared to the ASO brace and the no brace conditions.These results suggest that the tested ankle braces, especially the Element brace, provided effective restriction of ankle inversion during both passive and dynamic movements.

Total knee replacement (TKR) is commonly used to correct end-stage knee osteoarthritis. Unfortunately, difficulty with stair climbing often persists and prolongs the challenges of TKR patents. Complete understanding of loading at the knee is of great interest in order to aid patient populations, implant manufacturers, rehabilitation, and future healthcare research. Musculoskeletal modeling and simulation approximates joint loading and corresponding muscle forces during a movement. The purpose of this study was to determine if knee joint loadings following TKR are recovered to the level of healthy individuals, and determine the differences in muscle forces causing those loadings. Data from five healthy and five TKR patients were selected for musculoskeletal simulation. Variables of interest included knee joint reaction forces (JRF) and the corresponding muscle forces. A paired samples t-test was used to detect differences between groups for each variable of interest (p

[Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern.

Cycling is commonly prescribed for individuals with knee osteoarthritis (OA) but very little biomechanical research exists on the topic. Individuals with OA may be at greater risk of OA progression or other knee injuries because of their altered knee kinematics. This study investigated the effects of lateral wedges on knee joint biomechanics and pain in patients with medial compartment knee OA during stationary cycling. Thirteen participants with OA and 11 paired healthy participants volunteered for this study. A motion analysis system and a customized instrumented pedal were used to collect 5 pedal cycles of kinematics and kinetics, respectively, during 2 minutes of cycling in 1 neutral and 2 lateral wedge (5° and 10°) conditions. Participants pedaled at 60 RPM and an 80 W workrate and rated their knee pain on a visual analog scale during each minute of each condition. There was a 22% decrease in the internal knee abduction moment with the 10° wedge. However, this finding was not accompanied by a decrease in knee adduction angle or subjective pain. Additionally, there was an increase in vertical and horizontal pedal reaction force which may negate the advantages of the decreased internal knee abduction moment. For people with medial knee OA, cycling with 10° lateral wedges may not be sufficient to slow the progression of OA beyond the neutral riding condition.

Increased step widths have been shown to reduce peak internal knee abduction moments in healthy individuals but not in knee osteoarthritis patients during stair descent. This study aimed to assess effects of increased step widths on peak knee abduction moments and associated variables in adults with medial knee osteoarthritis and healthy older adults during stair ascent. Thirteen healthy older adults and 13 medial knee osteoarthritis patients performed stair ascent using preferred, wide, and wider step widths. Three-dimensional kinematics and ground reaction forces (GRFs) using an instrumented staircase were collected. Increased step width reduced first and second peak knee abduction moments, and knee abduction moment impulse. In addition, frontal plane GRF at time of first and second peak knee abduction moment and lateral trunk lean at time of first peak knee abduction moment were reduced with increased step width during stair ascent in both groups. Knee abduction moment variables were not different between knee osteoarthritis patients and healthy controls. Our findings suggest that increasing step width may be an effective simple gait alteration to reduce knee abduction moment variables in both knee osteoarthritis and healthy adults during stair ascent. However, long term effects of increasing step width during stair ascent in knee osteoarthritis and healthy adults remain unknown.

Background. Cervical orthoses are often prescribed for both extrication stabilization of trauma patients and a treatment option of injuries to the cervical spine. The objective of this study was to compare effectiveness of two new and two established cervical orthoses in restricting 3D range of motion in the cervical spine. Methods. Twenty healthy males and females (ten each) participated in the study. Two new cervical collars, C-Breeze and XTW and two established collars, Miami J and Aspen, were examined. A 3-camera Vicon system was used to collect 3D kinematic data. Subjects performed three trials in each of the 15 test conditions wearing no collar and the four cervical collars and performing three different head movements: flexion–extension, left–right lateral flexion, and left–right axial rotation. Findings. The results comparing with the unbraced movements indicated that the Miami J and C-Breeze collars had significantly greater percent reduction on range of motion in flexion than the XTW collar. For both extension and lateral bending, all three collars showed greater percent reduction than the Miami J. The XTW also showed greater reduction than the C-Breeze and Aspen in extension. Finally, the C-Breeze collar showed a significantly more reduction in axial rotation than the Miami J collar. Interpretation. The results suggested that C-Breeze and XTW along with the Miami J and Aspen collars are effective in restricting range of motion in the cervical spine. The two new cervical orthoses also performed either comparably as or better than the two established cervical orthoses.

Background Cycling is commonly prescribed for knee osteoarthritis, but previous literature on biomechanics during cycling and the effects of acute intervention on osteoarthritis patients does not exist. Due to their altered knee kinematics, osteoarthritis patients may be at greater risk of osteoarthritis progression or other knee injuries during cycling. This study investigated the effects of reduced foot progression (toe-in) angles on knee joint biomechanics in subjects with medial compartment knee osteoarthritis. Methods Thirteen osteoarthritis and 11 healthy subjects participated in this study. A motion analysis system and custom instrumented pedal was used to collect 5 pedal cycles of kinematic and kinetic data in 1 neutral and 2 toe-in conditions (5° and 10°) at 60 RPM and 80 W. Findings For peak knee adduction angle, there was a 61% (2.7°) and a 73% (3.2°) decrease in the 5° and 10° toe-in conditions compared to neutral in the osteoarthritis group and a 77% (1.7°) and 109% (2.4°) decrease in the healthy group for the 5° and 10° conditions, respectively. This finding was not accompanied by a decrease in pain or peak knee abduction moment. A simple linear regression showed a positive correlation between Kelgren–Lawrence score and both peak knee adduction angle and abduction moment. Interpretation For individuals who cycle with increased knee adduction angles, decreasing the foot progression angle may be beneficial for reducing the risk of overuse knee injuries during cycling by resulting in a frontal plane knee alignment closer to a neutral position.

Objective—To compare the 3-D motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament (CCL)–deficient stifle joints following tibial plateau leveling osteotomy (TPLO) or lateral fabellar–tibial suture (LFS) stabilization by use of an inverse dynamics method. Animals—6 clinically normal dogs and 19 dogs with CCL-deficient stifle joints that had undergone TPLO (n = 13) or LFS (6) stabilization at a mean of 4 and 8 years, respectively, prior to evaluation. Procedures—For all dogs, an inverse dynamics method was used to describe the motion of the pelvic limbs in the sagittal, frontal, and transverse planes. Motion and energy patterns for the hip, stifle, and tibiotarsal (hock) joints in all 3 planes were compared among the 3 groups. Results—Compared with corresponding variables for clinically normal dogs, the hip joint was more extended at the beginning of the stance phase in the sagittal plane for dogs that had a TPLO performed and the maximum power across the stifle joint in the frontal plane was greater for dogs that had an LFS procedure performed. Otherwise, variables in all planes were similar among the 3 groups. Conclusions and Clinical Relevance—Gait characteristics of the pelvic limb did not differ between dogs that underwent TPLO and dogs that underwent an LFS procedure for CCL repair and were similar to those of clinically normal dogs. Both TPLO and LFS successfully provided long-term stabilization of CCL-deficient stifle joints of dogs with minimal alterations in gait.

Background Research shows that one of the first complaints from knee osteoarthritis (OA) patients is difficulty in stair ambulation due to knee pain. Increased step width (SW) has been shown to reduce first and second peak internal knee abduction moments, a surrogate variable for medial compartment knee joint loading, during stair descent in healthy older adults. This study investigates the effects of increased step width (SW) on knee biomechanics and knee pain in medial compartment knee OA patients during stair descent. Methods Thirteen medial compartment knee OA patients were recruited for the study. A motion analysis system was used to obtain three-dimensional joint kinematics. An instrumented staircase was used to collect ground reaction forces (GRF). Participants performed stair descent trials at their self-selected speed using preferred, wide, and wider SW. Participants rated their knee pain levels after each SW condition. Results Increased SW had no effect on peak knee abduction moments and knee pain. Patients reported low levels of knee pain during all stair descent trials. The 2nd peak knee adduction angle and frontal plane GRF at time of 2nd peak abduction moment were reduced with increasing SW. Conclusions The findings suggest that increases in SW may not influence knee loads in medial compartment knee OA patients afflicted with low levels of knee pain during stair descent.

High- (HA) and low-arched (LA) athletes have an exaggerated risk of injury. Ankle joint stiffness is a potential underlying mechanism for the greater rate of injury within these two functionally different groups. An alternative candidate mechanism of injury in HA and LA athletes pertains to the efficacy of the foot as a rigid lever during propulsion. The purpose of this study was to quantify the differences in ankle dynamic joint stiffness, and ankle braking work and ankle propulsive work during stance phase of running. Methods Ten HA and ten LA athletes performed five barefoot running trials while ground reaction forces and three-dimensional kinematics were recorded. Ankle dynamic joint stiffness was calculated as the slope of the ankle joint moment–ankle joint angle plot during load attenuation. Ankle braking and propulsive work values were calculated for the stance phase. Results HA athletes had significantly greater ankle dynamic joint stiffness and significantly smaller ankle net and propulsive work than LA athletes. Conclusions These data demonstrate that HA and LA athletes exhibit unique biomechanical patterns during running. These patterns may be related to lower extremity injury.

Background Flip-flops and sandals are popular choices of footwear due to their convenience. However, the effects of these types of footwear on lower extremity biomechanics are still poorly understood. Therefore, the objective of this study was to investigate differences in ground reaction force (GRF), center of pressure (COP) and lower extremity joint kinematic and kinetic variables during level-walking in flip-flops, sandals and barefoot compared to running shoes. Methods Ten healthy males performed five walking trials in the four footwear conditions at 1.3 m/s. Three-dimensional GRF and kinematic data were simultaneously collected. Results A smaller loading rate of the 1st peak vertical GRF and peak propulsive GRF and greater peak dorsiflexion moment in early stance were found in shoes compared to barefoot, flip-flops and sandals. Barefoot walking yielded greater mediolateral COP displacement, flatter foot contact angle, increased ankle plantarflexion contact angle, and smaller knee flexion contact angle and range of motion compared to all other footwear. Conclusions The results from this study indicate that barefoot, flip-flops and sandals produced different peak GRF variables and ankle moment compared to shoes while all footwear yield different COP and ankle and knee kinematics compared to barefoot. The findings may be helpful to researchers and clinicians in understanding lower extremity mechanics of open-toe footwear.

Randomized controlled trial.To determine the effects of instruction to improve frontal plane knee biomechanics during a jump-landing task.Technique training is a common component of knee injury-prevention programs. In developing programs that minimize time commitment and increase the likelihood of adoption by target groups, there is a need to evaluate individual program components.A total of 26 female recreational athletes (average age, 21.2 years), who presented with medial knee displacement during a jump-landing task, completed the study protocol. Participants were randomly placed into 1 of 2 groups, an experimental or control group. The experimental group received instructions aimed at improving knee abduction during jump landings. The control group received a sham training. Prior to training, baseline kinematics and kinetics (peak knee abduction angle, peak internal knee adductor moment, knee flexion excursion, peak internal knee extensor moment, and peak vertical ground reaction force) were obtained from participants while performing a basketball rebound task. Immediate (5 minutes postinstruction) and delayed (15-20 minutes postinstruction) retention tests were performed within the instructional session. Two additional retention tests were performed following home-based training (1 and 2 weeks following the initial training).The initial instructional session resulted in greater knee flexion excursion (9°) and a 20% reduction in the peak internal knee adductor moment in the experimental group. Following home-based training, the experimental group continued to exhibit increased knee flexion excursion, along with decreased peak vertical ground reaction forces. No biomechanical changes were observed in the control group for any of the retention tests when compared to baseline.The jump-training instructions employed in the current study resulted in kinematic and kinetic changes in the sagittal plane as opposed to the frontal plane.Prevention, level 2b-.