Knee Power Generation Research Articles

Powered knee and ankle prostheses enable natural ambulation on level ground and stairs for individuals with bilateral above-knee amputation: a case study

Ambulation with existing prostheses is extremely difficult for individuals with bilateral above-knee amputations. Commonly prescribed prostheses are passive devices that cannot replace the biomechanical functions of the missing biological legs. As a result, most individuals with bilateral above-knee amputations can only walk for short distances, have a high risk of falling, and are unable to ascend stairs with a natural gait pattern. Powered prostheses have the potential to address this issue by replicating the movements of the biological leg. Previous studies with individuals with bilateral above-knee amputations have shown that walking with powered prostheses is possible. However, stair ambulation requires different kinematics, kinetics, and power than walking. Therefore, it is not known whether powered prostheses can restore natural ambulation on stairs for bilateral above knee individuals. Here we show a case study with an individual with bilateral above-knee amputations using a pair of lightweight powered knee and ankle prostheses for walking and stair ambulation. The kinematic analysis shows that powered prostheses can restore natural leg movements, enabling the individual to walk and climb stairs using different gait patterns, such as step-over-step or step-by-step, one step or two steps at a time. The kinetic analysis shows that the powered prostheses can restore natural ankle push-off in walking and positive knee power generation in stair ascent, which are fundamental biomechanical functions of the missing biological legs. This case study is a first step towards enhancing functional mobility and quality of life for individuals with bilateral above-knee amputations through powered knee and ankle prostheses.

Effect of Whole-Body Vibration Exercise on Power Profile and Bone Mineral Density in Postmenopausal Women With Osteoporosis: A Randomized Controlled Trial

ObjectiveThe purpose of this study was to investigate the effect of whole-body vibration (WBV) on muscle work and bone mineral density (BMD) of the lumbar vertebrae and femur in postmenopausal women. MethodsForty-three postmenopausal women with low BMD were randomly assigned to WBV and control groups. Both groups received calcium and vitamin D supplementations once daily, while the WBV group additionally received WBV exercise (twice/wk) for 24 successive weeks. Qualisys gait analysis system was used to measure hip power generation by hip extensors (H1S) and flexors (H3S), hip power absorption by hip flexors (H2S), knee power absorption by quadriceps during loading response (K1S) and preswing (K3S), knee power absorption by hamstring (K4S), knee power generation by quadriceps (K2S), ankle power absorption by dorsiflexors (A1S) and plantar flexors (A2S), and ankle power generation by plantar flexors (A3S). Also, dual-energy X-ray absorptiometry was used to measure BMD of the lumbar vertebrae and femur before and after the intervention. ResultsThere were significant increases (P < .05) in the hip muscle work (H1S, H2S, and H3S), knee muscle work (K1S, K2S, K3S, and K4S), ankle muscle work (A1S, A2S, and A3S) during gait, and BMD of the lumbar vertebrae and femur of the WBV group. However, there were no significant changes (P > .05) in the control group. The posttreatment values of the hip, knee, and ankle muscle work and BMD of the WBV group were significantly (P < .05) higher than the posttreatment values of the control group. ConclusionWhole-body vibration training improved the leg muscle work and lumbar and femoral BMD in postmenopausal women with low BMD.

Effect of consecutive jumping trials on metatarsophalangeal, ankle, and knee biomechanics during take-off and landing

This study examined the differences in single and consecutive jumps on ground reaction forces (GRF) as well as metatarsophalangeal (MTP), ankle and knee kinematics and kinetics during jumping take-off and landing. Eighteen basketball players performed countermovement jumps in both single and consecutive movement sessions. Synchronised force platform and motion capture systems were used to measure biomechanical variables during take-off and landing. Paired t-tests (or Wilcoxon signed-rank tests) were performed to examine any significant differences regarding mean and coefficient of variation in each of the variables tested. A Holm–Bonferroni correction was applied to P-values to control the false discovery rate of 5%. The findings indicated that consecutive jumps had lower jump height, take-off velocity and landing impact. During take-off, consecutive jumps demonstrated larger peak MTP and ankle extension velocities, knee extension moments as well as larger values for ankle and knee power generation; During landing, the consecutive jumps had larger peak MTP flexion angle, joint velocities (MTP, ankle and knee), and peak knee flexion moments and power absorption. Additionally, consecutive jumps had higher within-trial reliability (i.e. smaller CV) for peak MTP flexion angle at landing (P < 0.05), but lower reliability (i.e. higher CV) for peak knee flexion velocity and power absorption at landing. These results suggest that the consecutive jump trials led to distinct movement kinematics and higher loading responses in jump take-off and landing.

Gait biomechanics in joint hypermobility syndrome: a spatiotemporal, kinematic and kinetic analysis.

Joint hypermobility syndrome (JHS) symptoms of widespread joint hypermobility and pain, muscle weakness and reduced muscle-tendon stiffness suggest that there may be an impact on gait parameters. Identification of gait abnormalities may inform assessment and management. The objective in the present study was to use a cross-sectional designed study to explore the impact of JHS on gait parameters. A JHS group of 29 participants (mean age 37.57 (S.D. 13.77) years) was compared to a healthy control group of 30 participants (mean 39.27 (S.D. 12.59) years). Spatiotemporal parameters, joint kinematics and joint kinetics were captured using the Qualisys motion capture system synchronized with a Kistler force platform. Statistically significant reductions in walking speed, stride length and step length were found in the JHS group, while stance and double support durations were significantly increased (p < 0.01). During the swing phase, the JHS group showed significantly less knee flexion (p < 0.01). Reductions in hip extensor moment, and knee power generation and absorption were identified in the JHS group (p < 0.01). No other gait parameters were significantly altered. The JHS group walked more slowly with a kinematic 'stiffening' pattern. Hypermobility was not evident during gait. The observed stiffening pattern could be a strategy to avoid pain and improve balance. Impairments in moment and power generation could be related to several symptomatic and etiological factors in JHS. Clinicians should carefully consider gait in the assessment and management of people with JHS targeting the impairments identified by the current study.

Changes in Lower Extremity Energetics during Cutting in Chronic Ankle Instability Patients Following Rehabilitation Intervention

Energetic redistribution from the distal to proximal joints may be linked to sensorimotor deficits at the ankle in patients with chronic ankle instability (CAI). Little is known whether a rehab intervention improves lower extremity energetic patterns during cutting. PURPOSE: To examine the effect of a 6-week ankle and hip intervention program on ankle, knee and hip joint power during cutting in CAI patients. METHODS: 15 CAI subjects in a rehab group (23±2 yrs, 178±8 cm, 76±9 kg, 83±7% FAAM ADL, 56±10% FAAM Sports, 3.6±1.1 MAII, 4.7±2.0 ankle sprains) completed a series of 10 ankle and hip strength and proprioceptive exercises (theraband, wobble board, ankle disk, etc.) 3 times/week for 6 weeks under supervision. 14 CAI subjects participated in a control group (22±2 yrs, 177±9 cm, 75±12 kg, 81±9% FAAM ADL, 56±12% FAAM Sports, 3.4±1.2 MAII, 5.9±3.3 sprains). Subjects performed 10 jumps consisting of a max vertical jump plus a side cut. Functional analyses (α=.05) were used to detect a group x treatment interaction over time. If 95% CI did not cross the zero, significant differences existed. RESULTS: Figure 1. The rehab intervention resulted in up to (i) 0.8 W/kg less ankle power generation at 89-98% of stance, (ii) 2.9 W/kg more knee power absorption at 19-26% and 41-49% of stance, and 0.9 W/kg more knee power generation at 64-76% and 94-100% of stance, and (iii) 2.7 W/kg more hip power absorption at 2-5% and 17-25% stance and 1.6 W/kg less hip power absorption at 9-14% of stance. CONCLUSIONS: Relative to the control group, CAI patients in the rehab group tend to absorb power using the knee and hip during landing and to generate power using the knee during push-off. Proximal joints play a key role in landing energetics in patients with CAI following the intervention.Figure

Joint power generation differentiates young and adult sprinters during the transition from block start into acceleration: a cross-sectional study

The aim of this study was to investigate differences in joint power generation between well-trained adult athletes and young sprinters from block clearance to initial contact of second stance. Eleven under 16 (U16) and 18 under 18 (U18) promising sprinters executed an explosive start action. Fourteen well-trained adult sprinters completed the exact same protocol. All athletes were equipped with 74 spherical reflective markers, while an opto-electronic motion analysis system consisting of 12 infrared cameras (250 Hz, MX3, Vicon, Oxford Metrics, UK) and 2 Kistler force plates (1,000 Hz) was used to collect the three-dimensional marker trajectories and ground reaction forces (Nexus, Vicon). Three-dimensional kinematics, kinetics, and power were calculated (Opensim) and time normalised from the first action after gunshot until initial contact of second stance after block clearance. This study showed that adult athletes rely on higher knee power generation during the first stance to induce longer step length and therefore higher velocity. In younger athletes, power generation of hip was more dominant.

Quantitative gait analysis in parkin disease: Possible role of dystonia.

Parkin disease (PARK2, OMIM 602544) is an autosomal-recessive early-onset parkinsonism characterized by an early occurrence of lower limb dystonia. The aim of this study was to analyze spatiotemporal, kinematic, and kinetic gait parameters in patients with parkin disease in the OFF and ON conditions compared to healthy age-matched controls. Fifteen patients with parkin disease and 15 healthy age-matched controls were studied in a gait analysis laboratory with an integrated optoelectronic system. Spatiotemporal, kinematic, and kinetic gait parameters at a self-selected speed were recorded in the OFF and ON conditions. A jerk index was computed to quantify the possible reduction of smoothness of joint movements. Compared to controls, parkin patients had, either in the OFF or in the ON conditions, significant reduction of walking velocity, increased step width, and decreased percentage of double support. Kinematic analysis in both conditions showed: increased ankle dorsiflexion and knee flexion at the initial contact; maximal flexion and increased range of motion in mid stance; increased hip flexion and max extension in stance at pelvis; and increased mean tilt antiversion. Kinetics showed increased hip and knee power generation in stance in either condition. The jerk index was increased at all joints both in OFF and ON. There were no correlations between individual gait parameters and clinical ratings. Parkin patients have an abnormal gait pattern that does not vary between the OFF and the ON conditions. Variations recorded with instrumented analysis are more evident for kinematic than kinetic parameters at lower limbs. Severity of dystonia does not correlate with any individual kinematic parameter. © 2016 International Parkinson and Movement Disorder Society.

Control of propulsion and body lift during the first two stances of sprint running: a simulation study

The aim of this study was to relate the contribution of lower limb joint moments and individual muscle forces to the body centre of mass (COM) vertical and horizontal acceleration during the initial two steps of sprint running. Start performance of seven well-trained sprinters was recorded using an optoelectronic motion analysis system and two force plates. Participant-specific torque-driven and muscle-driven simulations were conducted in OpenSim to quantify, respectively, the contributions of the individual joints and muscles to body propulsion and lift. The ankle is the major contributor to both actions during the first two stances, with an even larger contribution in the second compared to the first stance. Biarticular gastrocnemius is the main muscle contributor to propulsion in the second stance. The contribution of the hip and knee depends highly on the position of the athlete: During the first stance, where the athlete runs in a forward bending position, the knee contributes primarily to body lift and the hip contributes to propulsion and body lift. In conclusion, a small increase in ankle power generation seems to affect the body COM acceleration, whereas increases in hip and knee power generation tend to affect acceleration less.

Quadriceps rate of force development affects gait and function in people with knee osteoarthritis

Quadriceps weakness exists in people with knee osteoarthritis (OA), but other muscle factors like rate of force development (RFD) may also be affected by knee OA. The purpose of this study was to determine if people with knee OA have deficits in quadriceps RFD, determine if quadriceps RFD would improve predicting knee joint power absorption and generation during free and fast walking, and determine if RFD would improve predicting functional outcomes. 26 subjects with knee OA and 23 healthy control subjects performed maximal voluntary isometric strength (MVIC) and RFD measures of the quadriceps. Subjects also underwent a 3-D motion analysis of both self-selected free and self-selected fast walking speeds. Joint kinetics were calculated from inverse dynamics. RFD was not different by group (p = 0.763), however, the OA subjects generated the highest peak RFD at a lower % MVIC (p = 0.008). Controls walked significantly faster at both free and fast walking speeds (p = 0.001, p = 0.029). Knee angles at heel strike and peak knee extension were lower (p = 0.004, p = 0.027) in the OA group. During fast walking knee power generation was higher in controls (p = 0.028). MVIC and force of highest peak RFD predicted KOOS-ADL score in the OA subjects, but only MVIC predicted stair climbing time. The submaximal force at which peak RFD occurs plays a significant role in knee joint power as well as functional measures in the OA subjects, providing further evidence that factors other than maximal strength are also important in people with knee OA.

Discrimination of Abnormal Gait Parameters Due to Increased Femoral Anteversion from other Effects in Cerebral Palsy

The effects of increased femoral anteversion (IFA) on gait pattern have a complex relationship with other orthopaedic and neurological abnormalities of cerebral palsy (CP). The aim of this study was to differentiate the effects of IFA from other factors in CP. The four groups in this study included: 15 typically developing children (Group: TDC) (age: 9.7 ± 0.5); 14 TDC with IFA (7.5 ± 1.7) (Group: TDC-IFA); 8 CP participants with IFA (age: 6.3 ± 1.7) (Group: CP IFA); and 10 CP participants with nearly normal femoral anteversion (age: 10.3 ± 4.7) (Group: CP-NFA). Altered peak knee-extension angle and stance-time, increased internal hip-rotation, internal foot-progression (p≤0.05) were influenced by IFA in both groups of CP-NFA and TDC-IFA. For the TDC groups; pelvic-rotation increased and peak knee and hip-extension, knee flexion-moment, peak knee-power generation in late-stance decreased among children with IFA (p≤0.05). For CP children; anterior pelvic-tilt, hip-flexion and peak knee-extension, hip power-absorbsion and generation, and peak knee power-absorsion (K3) increased and peak knee-flexion was delayed by IFA (p≤0.05). Therefore, IFA effects are different in CP and TDC. Peak knee-extension angle increased in TDC and decreased in CP with IFA. Besides the well known gait parameters related to IFA which are increased internal hip-rotation and foot-progression angle, it is recognised that peak knee-extension and stance-time are also influenced. Therefore, before muscle lengthening, femoral derotational osteotomy should be considered in the early stages of growth in CP to improve pelvic stability and the knee extensor mechanism.

Impact of Resistance Training on Balance and Gait in Multiple Sclerosis

Multiple sclerosis (MS) is an incurable neurodegenerative disease whose symptoms are only partially relieved by pharmaceutical intervention. Disability due to this disease process can impede activities of daily living and decrease quality of life, both for MS patients and for their care partners and families. A nonrandomized, nonblinded prospective cohort study of 45 patients with MS was undertaken to investigate the impact of an exercise program emphasizing resistance training on balance and gait. This article presents data for the first 33 participants to complete the study protocol. The exercise program consisted of twice-weekly 50-minute sessions for 6 months. At 3 months and 6 months, statistically significant improvements (P &amp;lt; .05) from baseline were observed for the following measures: Nine-Hole Peg Test, 2- and 3-second Paced Auditory Serial Addition Test, Modified Fatigue Impact Scale, NeuroCom Balance Master (NeuroCom International, Inc, Clackamas, OR), Timed Up and Go test, and Berg Balance Scale. Three-dimensional biomechanical gait analysis showed increased knee power generation during midstance and increased hip power generation during terminal stance. To determine whether individuals with varying levels of disability responded to exercise in a similar fashion, participants were divided into two subgroups based on Expanded Disability Status Scale score: little or no disability (EDSS score 1.0–4.0) and mild-to-moderate disability (EDSS score 4.5–6.5). No statistically significant differences in results were found. The results of this study indicate that participation in a resistance training program improves MS patients' ability to walk and to generate muscular forces during locomotion.

Joint torques and powers are reduced during ambulation for both limbs in patients with unilateral claudication

Symptomatic peripheral arterial disease (PAD) results in significant gait impairment. In an attempt to fully delineate and quantify these gait alterations, we analyzed joint kinematics, torques (rotational forces), and powers (rotational forces times angular velocity) in patients with PAD with unilateral claudication for both the affected and nonaffected legs. Twelve patients with unilateral PAD (age, 61.69 +/- 10.53 years, ankle-brachial index [ABI]: affected limb 0.59 +/- 0.25; nonaffected limb 0.93 +/- 0.12) and 10 healthy controls (age, 67.23 +/- 12.67 years, ABI >1.0 all subjects) walked over a force platform to acquire gait kinetics, while joint kinematics were recorded simultaneously. Data were collected for the affected and nonaffected limbs during pain free (PAD-PF) and pain induced (PAD-P) trials. Kinetics and kinematics were combined to quantify torque and powers during the stance period from the hip, knee, and ankle joints. The affected limb demonstrated significantly (P <.05) reduced ankle plantar flexion torque compared to controls during late stance in both PAD-PF and PAD-P trials. There were significant reductions in ankle plantar flexion power generation during late stance for both the affected (P <.05) and nonaffected limbs (P <.05) compared to control during PAD-PF and PAD-P trials. No significant differences were noted in torque comparing the nonaffected limbs in PAD-PF and PAD-P conditions to control for knee and hip joints throughout the stance phase. Significant reductions were found in knee power absorption in early stance and knee power generation during mid stance for both limbs of the patients with PAD as compared to control (P <.05). Patients with PAD with unilateral claudication demonstrate significant gait impairments in both limbs that are present even before they experience any claudication symptoms. Overall, our data demonstrate significantly reduced ankle plantar flexion torque and power during late stance with reduced knee power during early and mid stance for the affected limb. Further studies are needed to determine if these findings are dependent on the location and the severity of lower extremity ischemia and whether the changes in the nonaffected limb are the result of underlying PAD or compensatory changes from the affected limb dysfunction.

Compensatory advantages of toe walking

Kerrigan DC, Riley PO, Rogan S, Burke DT. Compensatory advantages of toe walking. Arch Phys Med Rehabil 2000;81:38-44. Objectives: The study’s hypothesis is that toe walking requires less peak muscle strength distally about the ankle and knee compared with normal heel-toe walking and thus may have compensatory advantages for patients with upper motor neuron injury and distal muscle weakness. Design: Motion analysis and force platform data were collected in able-bodied subjects during toe walking and normal walking. Sagittal plane joint torques reflecting muscle force requirements and joint powers reflecting nonisometric muscle contraction were compared between the two conditions using paired t tests, applying a Bonferroni correction for multiple comparisons. Setting: A gait laboratory. Subjects: Seventeen able-bodied adults, 9 of whom were ballet dancers. Main Outcome Measures: Peak hip, knee, and ankle joint torque and power variables during walking. Results: Peak ankle plantarflexor torque and ankle power generation during terminal stance and preswing were reduced (p < .001), as compared with normal heel-toe walking. The normal ankle dorsiflexor torque at initial contact and the knee extensor torque and knee power generation during loading response were all essentially absent during toe walking. Hip extensor torque and hip power generation during the loading response phase were greater for toe walking (p < .001). Conclusion: Toe walking may require less ankle plantarflexor, ankle dorsiflexor, and knee extensor strength than normal heel-toe walking and thus may have compensatory advantages for patients with upper motor neuron injury and distal lower extremity weakness. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation