Hip and knee frontal plane moments in persons with unilateral, trans-tibial amputation

Persons with unilateral, lower-extremity amputation are at risk of developing osteoarthritis in their intact limb. Among persons without amputation, knee osteoarthritis disease severity has been linked to elevated frontal plane knee moments. Therefore, the purpose of this study was to examine knee and hip frontal plane moments in persons with unilateral, trans-tibial amputation. We hypothesized that knee and hip internal abduction moments are greater in the intact limb compared to the prosthetic side. Three-dimensional gait mechanics were measured bilaterally from 10 persons with unilateral, trans-tibial amputation during walking to calculate lower-extremity joint moments. The intact limb knee and hip peak internal abduction moments were 46% and 39% greater, respectively, than on the prosthetic side. The intact side knee and hip peak internal abduction moments were 17% and 6% greater, respectively, than normal. Larger moments suggest joint loading is of higher magnitude on the intact side, which may be predisposed to premature joint degeneration, particularly knee osteoarthritis.     

The effects of symmetric and asymmetric foot placements on sit-to-stand joint moments

The purpose of this study was to determine the effects of symmetric and asymmetric foot placements on joint moments during sit-to-stand movements. Three symmetric (foot-neutral, foot-back, and foot-intermediate) and three asymmetric foot placements (preferred stagger, nonpreferred stagger, and intermediate stagger) were tested. Standard (46 cm) and low (41 cm) seat heights were chosen to represent an average public seat height and a 10% lower seat height. Using inverse dynamics, maximum ankle plantarflexion, knee extension, hip extension, and hip abduction moments were calculated. Hip extension moments were significantly increased when using foot-neutral as compared to foot-back. Ankle plantarflexion and knee extension moments were significantly increased when a foot was placed in the posterior position as compared to the anterior position for preferred and nonpreferred stagger. Knee extension moments were significantly increased at the low seat height as compared to the standard seat height. When shifting the feet anterior or posterior for symmetric placements during sit-to-stand, the most dramatic effect was an increase in hip extension moments when the feet are shifted anteriorly. Utilizing asymmetric foot placements during sit-to-stand produced increases in ankle plantarflexion and knee extension moments for the posteriorly placed limb, with reductions in the anteriorly placed limb.     

Frontal Plane Landing Mechanics in High-Arched Compared With Low-Arched Female Athletes

OBJECTIVE:: To examine ground reaction forces (GRFs); frontal plane hip, knee, and ankle joint angles; and moments in high-arched (HA) and low-arched (LA) athletes during landing. DESIGN:: Experimental study. SETTING:: Controlled research laboratory. PARTICIPANTS:: Twenty healthy female recreational athletes (10 HA and 10 LA). INTERVENTIONS:: Athletes performed 5 barefoot drop landings from a height of 30 cm. MAIN OUTCOME MEASURES:: Frontal plane ankle, knee, and hip joint angles (in degrees) at initial contact, peak vertical GRF, and peak knee flexion; peak ankle, knee, and hip joint moments in the frontal plane. RESULTS:: Vertical GRF profiles were similar between HA and LA athletes (P = 0.78). The HA athletes exhibited significantly smaller peak ankle inversion angles than the LA athletes (P = 0.01) at initial contact. At peak vertical GRF, HA athletes had significantly greater peak knee (P = 0.01) and hip abduction angles than LA athletes (P = 0.02). There were no significant differences between HA and LA athletes in peak joint moments (hip: P = 0.68; knee: P = 0.71; ankle: P = 0.15). CONCLUSIONS:: These findings demonstrate that foot type is associated with altered landing mechanics, which may underlie lower extremity injuries. The ankle-driven strategy previously reported in female athletes suggests that foot function may have a greater relationship with lower extremity injury than that in male athletes. Future research should address the interaction of foot type and gender during landing tasks.     

Age-related joint moment characteristics during normal gait and successful reactive-recovery from unexpected slip perturbations

The objective of the current study was to investigate the effects of aging on 3D lower extremity joint moments during successful reactive-recovery from unexpected slips. Unexpected slips were induced by having participants walk over a slippery floor surface. Successful reactive-recovery trials from nine young and nine elderly participants were identified and analyzed. Three-dimensional inverse dynamics were implemented to calculate reactive joint moments at the ankle, knee, and hip joints. Peak joint moment magnitude and the speed of peak joint moment generation were used to describe the balance recovery strategies from unexpected slips. Results indicated significantly higher peak joint moments in recovery than in normal walking for both the young and elderly. Meanwhile, during reactive-recovery, the elderly were found to utilize both frontal and sagittal joint moments while the younger adults relied primarily on sagittal joint moment. It was concluded that the ankle and knee joints were critical in controlling sagittal plane motion disturbance, while the hip joint was mainly responsible for stabilizing upper body balance in the frontal plane. This study confirmed age-related differences in joint moment generation during unexpected slips. Additionally, implementing 3D analysis is recommended in future slips and falls research.     

Effects of infant transportation on lower extremity joint moments: Baby carrier versus carrying in-arms

BackgroundThe act of babywearing is recognizably a task of load carriage and has gained popularity among millennial caregivers.Research QuestionThe implications of babywearing on lower extremity joint moments of the caregiver are still unknown during prolonged transport and a direct comparison of babywearing to carrying an infant in-arms has not been previously conducted.MethodsEighteen females participated in this study by performing 3 conditions: a) 3 min walking unloaded (UL), b) 15 min walking while carrying a mannequin infant in-arms (IA), and c) 15 min walking while wearing a mannequin infant in an anteriorly positioned baby carrier (BC). Two separate data analyses were conducted using a repeated measures ANOVA. First, UL compared to the initial minute of walking for IA and BC. Second, UL compared to the final minute of walking for IA and BC.ResultsDuring initial minute comparisons, both IA and BC conditions increased joint moments in the frontal and sagittal plane at the knee with no change at the ankle and hip. During final minute comparisons, IA maintained the increases in the knee frontal plane joint moments observed during initial minute comparisons but also increased at the hip; however, BC generally showed no statistical difference from UL. Carrying an infant in a baby carrier more closely resembles unloaded walking, while carrying an infant in-arms appears to increase the mechanical load placed on the knee and hip joints in the frontal plane through an increase in joint moments.SignificanceDuring prolonged transportation, caregivers might choose to employ a baby carrier as opposed to carrying an infant in-arms, as in-arm carriage increases the loading knee abduction moment by 8.7% and the loading knee extension moment by 16.7%.     

The influence of heel height on utilized coefficient of friction during walking

Wearing high heel shoes has been associated with an increased potential for slips and falls. The association between wearing high heels and the increased potential for slipping suggests that the friction demand while wearing high heels may be greater when compared to wearing low heel shoes. The purpose of this study was to determine if heel height affects utilized friction (uCOF) during walking. A secondary purpose of this study was to compare kinematics at the ankle, knee, and hip that may explain uCOF differences among shoes with varied heel heights. Fifteen healthy women (mean age 24.5 ± 2.5 yrs) participated. Subjects walked at self-selected velocity under 3 different shoe conditions that varied in heel height (low: 1.27 cm, medium: 6.35 cm, and high: 9.53 cm). Ground reaction forces (GRFs) were recorded using a force platform (1560 Hz). Kinematic data were obtained using an 8 camera motion analysis system (120 Hz). Utilized friction was calculated as the ratio of resultant shear force to vertical force. One-way repeated measures ANOVAs were performed to test for differences in peak uCOF, GRFs at peak uCOF and lower extremity joint angles at peak uCOF. On average, peak uCOF was found to increase with heel height. The increased uCOF observed in high heel shoes was related to an increase in the resultant shear force and decrease in the vertical force. Our results signify the need for proper public education and increased footwear industry awareness of how high heel shoes affect slip risk.     

Kinetics of the lower limb during two typical Tai Chi movements in the elderly

Tai Chi (TC) is a recommended exercise for elderly people; however, its loading on the joints of the lower limbs is unknown. This study examined the 3D kinetics of the lower limbs during two typical TC movements and walking in the elderly. Fifteen experienced TC practitioners participated. Ground reaction forces, joint moments and time-to-peak joint moment generation were analysed. Compared with walking, both TC movements generated significantly (1) smaller peak ground reaction forces in all directions, except the anterior; (2) larger hip extension, adduction and internal rotational moments, knee adduction/abduction and internal rotation moments and eversion/inversion and external/internal moments of ankle–foot; and (3) longer peak moment generation time for hip extension, adduction and internal rotation, knee extension and ankle dorsiflexion and inversion. The TC loading patterns are consistent with the mechanical behaviour of biological tissues, which could help to strengthen the lower extremities and prevent falls in the elderly.     

Dynamic loading of the knee and hip joint and compensatory strategies in children and adolescents with varus malalignment

Three-dimensional gait analysis is a diagnostic tool that can be used to gain a better understanding of the relationship between joint loading and the onset or progression of articular cartilage degeneration in subjects with varus malalignment. The purpose of the present study was to investigate knee and hip joint angles and moments in children and adolescents with pathological varus alignment of the knee without signs of knee osteoarthritis (OA). Moreover, we wanted to know if compensatory mechanisms are present in this young patient group. Fourteen, otherwise healthy patients with varus malalignment of the knee and 15 healthy control subjects were analysed. Patients showed a reduced knee extension and a significantly lower maximum knee extension moment in terminal stance compared to controls. The maximum knee adduction moment in mid and terminal stance and the maximum hip abduction moment in loading response were significantly higher in the patient group. In the transverse plane, abnormally increased knee internal rotation and hip external rotation moments were present in patients with varus malalignment. These findings imply that varus malalignment is not an isolated problem in the frontal plane. In contrast to adult patients with established medial knee OA, the young patients assessed in the present study did not show typical compensatory mechanisms such as increased foot progression angle or reduced walking speed. This suggests that children and adolescents with varus malalignment of the knee probably do not need to alter their spatio-temporal gait parameters in order to decrease knee joint loading.     

Effects of obesity on the biomechanics of walking at different speeds

PURPOSE: Walking is a recommended form of exercise for the treatment of obesity, but walking may be a critical source of biomechanical loads that link obesity and musculoskeletal pathology, particularly knee osteoarthritis. We hypothesized that compared with normal-weight adults 1) obese adults would have greater absolute ground-reaction forces (GRF) during walking, but their GRF would be reduced at slower walking speeds; and 2) obese adults would have greater sagittal-plane absolute leg-joint moments at a given walking speed, but these moments would be reduced at slower walking speeds. METHODS: We measured GRF and recorded sagittal-plane kinematics of 20 adults (10 obese and 10 normal weight) as they walked on a level, force-measuring treadmill at six speeds (0.5-1.75 m.s(-1)). We calculated sagittal-plane net muscle moments at the hip, knee, and ankle. RESULTS: Compared with their normal-weight peers, obese adults had much greater absolute GRF (N), stance-phase sagittal-plane net muscle moments (N.m) and step width (m). CONCLUSIONS: Greater sagittal-plane knee moments in the obese subjects suggest that they walked with greater knee-joint loads than normal-weight adults. Walking slower reduced GRF and net muscle moments and may be a risk-lowering strategy for obese adults who wish to walk for exercise. When obese subjects walked at 1.0 versus 1.5 m.s(-1), peak sagittal-plane knee moments were 45% less. Obese subjects walking at approximately 1.1 m.s(-1) would have the same absolute peak sagittal-plane knee net muscle moment as normal-weight subjects when they walk at their typical preferred speed of 1.4 m.s(-1).     

Association between isometric muscle strength and gait joint kinetics in adolescents and young adults with cerebral palsy

The purpose of this study was to determine the association between isometric muscle strength of the lower limbs and gait joint kinetics in adolescents and young adults with cerebral palsy (CP). Twenty-five participants (11 males) with bilateral spastic CP, aged 14-22 years (mean: 18.9, sd: 2.0 yr) and Gross Motor Function Classification System (GMFCS) level II (n=19) and III (n=6) were tested. Hand held dynamometry was used to measure isometric strength (expressed in Nm/kg) of the hip, knee, and ankle muscles using standardized testing positions and procedures. 3D gait analysis was performed with a VICON system to calculate joint kinetics in the hip, knee and ankle during gait. Ankle peak moments exceeded by far the levels of isometric strength of the plantar flexors, while the knee and hip peak moments were just at or below maximal isometric strength of knee and hip muscles. Isometric muscle strength showed weak to moderate correlations with peak ankle and hip extension moment and power during walking. Despite considerable muscle weakness, joint moment curves were similar to norm values. Results suggest that passive stretch of the muscle-tendon complex of the triceps surae contributes to the ankle moment during walking and that muscle strength assessment may provide additional information to gait kinetics.     

Increased knee flexion and varus moments during gait with high-heeled shoes: A systematic review and meta-analysis

BackgroundHigh-heeled shoes have been thought to alter lower extremity joint mechanics during gait, however its effects on the knee remain unclear.Research questionThis systematic review and meta-analysis aimed to determine the effects of high-heeled shoes on the sagittal- and frontal-plane knee kinetics/kinematics during gait.Methods1449 studies from 6 databases were screened for the following criteria: 1) healthy adult females, 2) knee joint kinematics/kinetics reported for the early stance phase during gait under varying shoe heel heights (including barefoot). Excluded studies included those mixing different shoe styles in addition to altering the heel heights. A total of 14 studies (203 subjects) met the selection criteria, resulting in 51 and 21 Cohen’s d effect sizes (ESs) comparing the differences in knee sagittal- (flexion) and frontal-plane (varus) moment/angle, respectively, between shoes with higher heels and shoes with lower heels/barefoot.ResultsMeta-analyses yielded a significant medium-to-large effect of higher heels compared to lower heels on increasing knee flexion moment (overall ES = 0.83; P < 0.01), flexion angle (overall ES=0.46; P < 0.01), and varus moment (overall ES=0.52; P < 0.01) during the early stance phase of gait. The results of meta-regressions used to explore factors explaining the heterogeneity among study ESs revealed that a greater ES in the knee flexion moment was associated with an elevated heel height of the high-heeled shoes (P = 0.02) and greater body mass of the individuals (P = 0.012). A greater ES in the knee varus moment during high-heeled gait was associated with a greater body height (P = 0.003) and mass (P = 0.006).SignificanceGiven the association between increased knee flexion/varus moments and risk of developing knee osteoarthritis (OA), women who wear high-heel shoes frequently and for a long period may be more susceptible to knee OA. Preventive treatments, such as lower extremity muscle strengthening, may help improve shock absorption to decrease knee loading in high-heel users.     

Is there a dose-response of medial wedge insoles on lower limb biomechanics in people with pronated feet during walking and running?

BackgroundAlthough the effects of medial wedge insoles on lower limb biomechanics have been investigated, information about the effects of different magnitudes of medial posting is still lacking.Research questionWhat are the dose-response effects of medial wedge insoles with postings varying between 0 °, 3 °, 6 °, and 9 ° of inclination on the lower limb biomechanics during walking and running in individuals with pronated feet?MethodsSixteen participants with an FPI ≥ 6 were recruited. Four arch-supported insole conditions with varying degrees of medial heel wedge were tested (0°, 3°, 6°, and 9°). A 3D motion analysis system with force plates was used to obtain the kinetics and kinematics of walking and running at self-selected speeds. To compare the ankle, knee, and hip angles and moments among conditions, a time series analysis was performed using Statistical Parametric Mapping (SPM).ResultsA reduction in ankle eversion angle was observed during walking for all insoles. For running, the 6° and 9° insoles decreased the ankle eversion angle during early stance and increased this angle during the propulsive phase. A decrease in ankle eversion moment was observed in walking and running for 6° and 9° insoles. An increase in knee adduction moment occurred in walking and running for all insoles. For hip, the 6° and 9° insoles showed, during walking, a decrease in hip adduction angle and an increase in hip adduction and external rotation moments. For most variables, statistical differences were found for a greater period across the stance phase as the medial wedge increased, except for ankle eversion moment and hip external rotation moment during walking.SignificanceThe biomechanical effects over the time series for many of the parameters increased with the addition of insole inclination, showing a dose-response effect of medial wedge insoles on the lower limb biomechanics during walking and running in adults with excessive foot pronation.     

Contributions of lower extremity joints to energy dissipation during landings

PURPOSE: The purpose of the study was to investigate changes in lower extremity joint energy absorption for different landing heights and landing techniques. METHODS: Nine healthy, active male subjects volunteered to perform step-off landings from three different heights (0.32 m, 2.5 m(-s); 0.62 m, 3.5 m(-s); and 1.03 m, 4.5 m(-s)) using three different landing techniques (soft, SFL; normal, NML; and stiff landing, STL). Each subject initially performed five NML trials at 0.62 m to serve as a baseline condition and subsequently executed five trials in each of the nine test conditions (3 heights x 3 techniques). RESULTS: The results demonstrated general increases in peak ground reaction forces, peak joint moments, and powers with increases in landing height and stiffness. The mean eccentric work was 0.52, 0.74, and 0.87 J x kg(-1) by the ankle muscles, and 0.94, 1.31, and 2.15 J x kg(-1) by the hip extensors, at 0.32, 0.62, and 1.03 m, respectively. The average eccentric work performed by the knee extensors was 1.21, 1.63, and 2.26 J x kg(-1) for the same three heights. CONCLUSIONS: The knee joint extensors were consistent contributors to energy dissipation. The ankle plantarflexors contributed more in the STL landings, whereas the hip extensors were greater contributors during the SFL landings. Also a shift from ankle to hip strategy was observed as landing height increased.     

Lower extremity joint moments throughout gait at two speeds more than 4 years after ACL reconstruction

BackgroundLong-term gait adaptations after anterior cruciate ligament reconstruction (ACLR) have been reported. However, it is still unclear if they persist more than 4 years after surgery and if they are affected by gait speed.Research question: To investigate differences between groups, legs and walking speeds for ankle, knee and hip joint moments in three planes throughout the stance phase of gait.MethodsReconstructed participants (n = 20 males, 32.5 years, 5.5 years post-ACLR) and healthy controls (n = 20 males, 30.6 years) took part in the study. Gait analysis was performed in two different speeds (self-selected and 30% faster). Sagittal, frontal and transverse plane external moments were measured for ankle, knee and hip and compared throughout the stance phase using 95% confidence intervals. Significant differences were established as a consecutive 5% of gait cycle in which 95% confidence interval did not overlap.ResultsThe reconstructed leg did not demonstrate higher joint moments; there were largely no differences while there was lower knee external rotation moment compared to the non-preferred leg of the control group. Higher joint moments were observed during fast speed walking on sagittal plane for knee and hip moments in both groups, and in the frontal and transverse plane for ankle moments.SignificanceGait kinetics appear to be largely normalized at a minimum of 4 years after ACLR. Faster walking speed increase lower extremity joint moments.     

Mechanisms contributing to different joint moments observed during human walking

The present study investigated factors that contribute to the formation of a previously reported knee joint flexor moment during the stance phase of walking. Contradictory results have been reported on this flexor moment, which some but not all individuals exhibit. Seven healthy male subjects were high speed filmed while walking across a force platform, and EMG recordings were obtained from five leg muscles. To investigate segment interactions, net joint moments about the ankle, knee and hip joint were calculated by inverse dynamics and each term in the equation used for the moment calculation was evaluated during the timeecourse of the step cycle. To test the hypothesis that net joint moments are balanced by an external moment formed by the resulting ground reaction vector multiplied by the perpendicular distance to the actual joint, external moment arms were calculated by the floor reaction force vector approach (FRFV). Contrasting two subjects with different net joint moments about the knee and ankle joint revealed that the knee joint flexor moment could not be explained by an opposite external moment. The external moments were calculated by a simplified method (FRFV) in which the point of force application is incorrect for joints above the ankle joint. However, at the ankle joint the net joint moment was always opposed by an external moment of opposite polarity. A detailed examination of the equation used for the net joint moment calculation showed that a knee joint flexor moment can be caused directly by a large plantar flexor moment about the ankle joint. For example, the soleus muscle can pull the tibia and generate an extensor moment about the knee joint, which in turn has to be opposed by a knee flexor moment from the hamstring muscles. Otherwise the desired joint angles cannot be obtained during human walking. It is therefore suggested that the kinematics regarding how the foot is placed on the ground may influence the net ankle joint moment, while the moment patterns about the knee and hip joint are determined by segment interaction and the requirements for controlling the direction of the resulting ground reaction vector. In vertical jumping it is advantageous to generate extensor moments about the knee and hip joint simultaneously, while in horizontal locomotion this would result in inefficient vertical movements.     

The effect of tibiotalar alignment on coronal plane mechanics following total ankle replacement

BackgroundGait mechanics following total ankle replacement (TAR) have reported improved ankle motion following surgery. However, no studies have addressed the impact of preoperative radiographic tibiotalar alignment on post-TAR gait mechanics. We therefore investigated whether preoperative tibiotalar alignment (varus, valgus, or neutral) resulted in significantly different coronal plane mechanics or ground reaction forces post-TAR.MethodsWe conducted a non-randomized study of 93 consecutive end-stage ankle arthritis patients. Standard weight-bearing radiographs were obtained preoperatively to categorize patients as having neutral (±4°), varus (≥5° of varus), or valgus (≥5° of valgus) coronal plane tibiotalar alignment. All patients underwent a standard walking assessment including three-dimensional lower extremity kinetics and kinematics preoperatively, 12 and 24 months postoperatively.ResultsA significant group by time interaction was observed for the propulsive vertical ground reaction force (vGRF), coronal plane hip range of motion (ROM) and the peak hip abduction moment. The valgus group demonstrated an increase in the peak knee adduction angle and knee adduction angle at heel strike when compared to the other groups. Coronal plane ankle ROM, knee and hip angles at heel strike, and the peak hip angle exhibited significant increases across time. Peak ankle inversion moment, peak knee abduction moment and the weight acceptance vGRF also exhibited significant increases across time. Neutral ankle alignment was achieved for all patients by 2 years following TAR.ConclusionsRestoration of neutral ankle alignment at the time of TAR in patients with preoperative varus or valgus tibiotalar alignment resulted in biomechanics similar to those of patients with neutral preoperative tibiotalar alignment by 24-month follow-up.     

Effect of contralateral cane use on hip moment impulse in the frontal plane during the stance phase

BackgroundRecent reports have shown that the daily cumulative moment in the frontal plane (i.e., product of hip moment impulse in the frontal plane during the stance phase and mean steps per day) is a risk factor for hip osteoarthritis. This study aimed to clarify the effect of contralateral cane use on hip moment impulse in the frontal plane of the stance limb.MethodsThis study included 15 healthy subjects who walked under four experimental conditions: (1) without a cane and (2–4) contralateral cane use with 10%, 15%, and 20% body weight support (BWS), respectively. To maintain the same walking speed in all conditions, the cadence was set to 80 steps/min, and the step length was fixed. The hip moment impulses in the frontal plane (i.e., area under the hip ab-adduction moment waveform) and peak hip adduction moments in all conditions were calculated.ResultsContralateral cane use significantly decreased the hip moment impulse in the frontal plane and peak hip adduction moment compared to non-cane use. Moreover, the hip moment impulse in the frontal plane and peak hip adduction moment decreased significantly with increased cane BWS. There were no significant differences in walking speed, cadence, and step length between the four conditions.ConclusionContralateral cane use decreases the hip moment impulse in the frontal plane and peak hip adduction moment in the stance limb. These findings may help clarify how to delay the progression of hip osteoarthritis.     

Gait pattern in rheumatoid arthritis

The purpose of this study was to analyse kinematic and kinetic gait changes in rheumatoid arthritis (RA) patients in comparison to healthy controls and to examine whether levels of functional disability (Health Assessment Questionnaire (HAQ)-scores) were associated with gait parameters. Using a three-dimensional motion analysis system, kinematic and kinetic gait parameters were measured in 50 RA patients and 37 healthy controls. There was a significant reduction in joint motions, joint moments and work in the RA cohort compared with healthy controls. The following joint motions were decreased: hip flexion-extension range (Delta6 degrees ), hip abduction (Delta4 degrees ), knee flexion-extension range (Delta8 degrees ) and ankle plantarflexion (Delta10 degrees ). The following joint moments were reduced: hip extensor (Delta0.30Nm/kg) and flexor (Delta0.20Nm/kg), knee extensor (Delta0.11Nm/kg) and flexor (Delta0.13Nm/kg), and ankle plantarflexor (Delta0.44Nm/kg). Work was lower in hip positive work (Delta0.07J/kg), knee negative work (Delta0.08J/kg) and ankle positive work (Delta0.15J/kg). Correlations were fair although significant between HAQ and hip flexion-extension range, hip abduction, knee flexion-extension range, hip abductor moment, stride length, step length and single support (r=-0.30 to -0.38, p<0.05). Our findings suggest that RA patients have overall less joint movement and specifically restricted joint moments and work across the large joints of the lower limbs during walking than healthy controls. There were only fair associations between levels of functional disability and gait parameters. The findings of this study help to improve the understanding how RA affects gait changes in the lower limbs.     

Knee moment profiles during walking: errors due to soft tissue movement of the shank and the influence of the reference coordinate system.

The effect soft tissue movement of the shank had on knee joint moments during natural cadence walking was investigated in this study. This was examined by comparing knee moments determined from bone-anchored and surface mounted tracking targets. Six healthy adult subjects participated in this study. The largest difference (3 N m) occurred about the AP axis, with smaller differences of approximately 2 and 1 N m about the flexion/extension (F/E) and longitudinal (Long) axes, respectively. The magnitude of these differences would not likely affect the clinical interpretation of the data. The effect of reporting knee moments in two different orthogonal reference systems was also examined. The peak extension moment was significantly greater when expressed about an anatomical axis following the line of the malleoli than when the moment was reported about an axis parallel to the frontal plane of the shank. In contrast, the first peak abduction moment was significantly greater when expressed about an axis perpendicular to the frontal plane of the shank. Care should therefore be exercised whenever comparisons between studies are made in which the reference axes are not aligned.     

Evidence of compensatory joint kinetics during stair ascent and descent in Parkinson’s disease

BackgroundStair ambulation is a challenging activity of daily life that requires larger joint moments than walking. Stabilisation of the body and prevention of lower limb collapse during this task depends upon adequately-sized hip, knee and ankle extensor moments. However, people with Parkinson’s disease (PD) often present with strength deficits that may impair their capacity to control the lower limbs and ultimately increase their falls risk.ObjectiveTo investigate hip, knee and ankle joint moments during stair ascent and descent and determine the contribution of these joints to the body’s support in people with PD.MethodsTwelve PD patients and twelve age-matched controls performed stair ascent and descent trials. Data from an instrumented staircase and a three-dimensional motion analysis system were used to derive sagittal hip, knee and ankle moments. Support moment impulses were calculated by summing all extensor moment impulses and the relative contribution of each joint was calculated.ResultsLinear mixed model analyses indicated that PD patients walked slower and had a reduced cadence relative to controls. Although support moment impulses were typically not different between groups during stair ascent or descent, a reduced contribution by the ankle joint required an increased knee joint contribution for the PD patients.ConclusionsDespite having poorer knee extensor strength, people with PD rely more heavily on these muscles during stair walking. This adaptation could possibly be driven by the somewhat restricted mobility of this joint, which may provide these individuals with an increased sense of stability during these tasks.