Knee Flexor Moments Research Articles

Braking and propulsive impulses increase with speed during accelerated and decelerated walking

The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior–posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from 10 healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0–1.8m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects’ preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking.

Kinetics and kinematics analysis of incremental cycling to exhaustion

Technique changes in cyclists are not well described during exhaustive exercise. Therefore the aim of the present study was to analyze pedaling technique during an incremental cycling test to exhaustion. Eleven cyclists performed an incremental cycling test to exhaustion. Pedal force and joint kinematics were acquired during the last three stages of the test (75%, 90% and 100% of the maximal power output). Inverse dynamics was conducted to calculate the net joint moments at the hip, knee and ankle joints. Knee joint had an increased contribution to the total net joint moments with the increase of workload (5–8% increase, p < 0.01). Total average absolute joint moment and knee joint moment increased during the test (25% and 39%, for p < 0.01, respectively). Increases in plantar flexor moment (32%, p < 0.01), knee (54%, p < 0.01) and hip flexor moments (42%, p = 0.02) were found. Higher dorsiflexion (2%, for p = 0.03) and increased range of motion (19%, for p = 0.02) were observed for the ankle joint. The hip joint had an increased flexion angle (2%, for p < 0.01) and a reduced range of motion (3%, for p = 0.04) with the increase of workload. Differences in joint kinetics and kinematics indicate that pedaling technique was affected by the combined fatigue and workload effects.

Reactive Control and its Operation Limits in Responding to a Novel Slip in Gait

The purposes of this study were: (1) to examine the reactive control of the resultant joint moments at the lower limbs in response to a novel and unannounced slip; (2) to establish individualized forward-dynamics models; and (3) to explore personal potential by determining the operation limits of these moments at each lower limb joint, beyond which the resulting motion at this or other joints will exceed its/their normal range(s). Ten young subjects' kinematics and kinetics, collected during regular walking and during their first exposure to a novel and unannounced slip, were randomly selected from an existing database. An inverse-dynamics approach was applied to derive their (original) resultant joint moments, which were then used as input to establish forward-dynamics models, each including an individualized 16-element foot model to simulate ground reaction force. A simulated annealing (SA) algorithm was applied to modify the original moments, so that the subsequent output (baseline) moments can closely reproduce these subjects' recorded motion. A systematic alteration of the baseline moments was employed to determine the operation limits. The results revealed that the subjects reactively increased the hip extensor and knee flexor moments and reduced their ankle plantar flexor moments of their single-stance limb following slip onset. The "baseline" correction of the original moments can reach as much as 21% of the original moments. The analysis of the operation limits revealed that these individuals may be able to further increase their knee flexors more so than increase the hip extensors or reduce ankle plantar flexors before causing abnormal joint movement. Such systematic approach opens the possibility to properly assess an individual's rehabilitation potential, and to identify whether this person's strength is the limiting factor for stability training.

Gait and neuromuscular adaptations after using a feedback-based gait monitoring knee brace

Purpose The purpose of this study was to evaluate the gait and neuromuscular effects of a feedback-based gait monitoring knee brace. The aim of this paper was to explore how training with this knee brace affected the gait pattern utilized, rate of loading (ROL), and proprioceptive acuity. Methods Fifteen healthy women wore this knee brace that provided audible feedback on gait kinematics for a 30-min training period. We performed pre- and post-gait analyses and proprioceptive acuity assessments to determine gait learning and adaptation with this training. Results Post-training significant changes were seen in the knee angle prior to and at initial contact and peak knee extensor, flexor, and adductor moments, which ultimately led to a reduced ROL experienced. Subjects also had improved proprioceptive acuity post-training. Interpretations Our results indicate that using a feedback-based gait monitoring knee brace can change the gait pattern by increasing the knee flexion angle during the swing to stance transition. Though there was an approximate 25% decrease in the ROL experienced, there was also an increase in the knee adductor moment. Future long-term studies are needed to further explore the positive and negative effects of feedback-based gait monitoring knee brace on individuals with a compromised knee joint, such as those post-anterior cruciate ligament injury.

Knee kinetics during walking at different speeds in people who have undergone total knee replacement

Previous research suggests that most people who have undergone total knee replacement (TKR) walk with a sagittal knee moment profile and peak knee moments that are different from normal. However, most previous research has consisted of small samples of patients with prostheses that are no longer in use. The aim of this study was to compare the peak knee moments and patterns of the moment waveforms of walking at different speeds between a large cohort of TKR patients with the Genesis-II PS prosthesis (Smith and Nephew, Memphis, USA) and matched control participants. Forty patients 12 months following TKR and 40 control participants were assessed during walking at self-selected comfortable and fast speeds using motion analysis. Individual sagittal plane knee moment graphs were assessed for the presence of a biphasic pattern. Peak sagittal and coronal plane knee moments were compared between groups using a univariate ANOVA with walking speed as a covariate. A biphasic moment pattern was present in 87% and 92% of TKR patients when walking at comfortable and fast speeds, respectively. The knee flexor ( p < 0.001 at both speeds), extensor ( p = 0.004 at comfortable speed and p < 0.001 at fast speed) and adductor ( p < 0.001 at both speeds) moments were reduced in the TKR patients. The high proportion of TKR patients with biphasic moment patterns was unexpected, but suggests that modern prostheses can result in more normal outcomes. Nonetheless, the peak knee moments of patients were reduced compared to controls. Although these reductions may be beneficial to the survival of the prosthesis, these abnormalities may also indicate suboptimal functional outcome from TKR.

Erratum to: Robot-assisted modifications of gait in healthy individuals

Average ratio in integrated hip extensor and knee flexor moments between each of the post-training tests and the baseline test. Values greater or less than 1.0 indicate an increase or decrease, respectively, of the joint moment relative to the baseline test. FFC ? VG force-field constraint plus visual guidance, FFC force-field constraint, VG visual guidance, IPT immediate post-training, R1 retention 1, R2 retention 2. Error bars represent SEM

Stationary Cycling and Children with Cerebral Palsy: Case Reports for Two Participants

ABSTRACTThese case reports describe a stationary cycling intervention and outcomes for two child participants (P1 and P2) with spastic diplegic cerebral palsy. Each child completed a 12-week, 30-session cycling intervention consisting of strengthening and cardiorespiratory fitness phases. P1 exhibited higher training intensities, particularly during the cardiorespiratory phase. Average training heart rates were 59% and 35% of maximum heart rate for P1 and P2, respectively. Lower extremity peak knee flexor and extensor moments, gross motor function (Gross Motor Function Measure (GMFM-66)), preferred walking speed (thirty-second walk test), and walking endurance (600-yard walk-run test) were measured pre- and postintervention. Changes in outcome measurements corresponded with differences in exercise intensity. Greater gains in peak knee extensor moments, GMFM-66 scores (+4.2 versus +0.9), 600-yard walk-run test (−29% versus 0%) occurred for P1 versus P2, respectively. Preferred walking speeds did not increase substantially for P1 and decreased for P2.

Pediatric Endurance and Limb Strengthening (PEDALS) for Children With Cerebral Palsy Using Stationary Cycling: A Randomized Controlled Trial

Effective interventions to improve and maintain strength (force-generating capacity) and endurance are needed for children with cerebral palsy (CP). This study was performed to examine the effects of a stationary cycling intervention on muscle strength, locomotor endurance, preferred walking speed, and gross motor function in children with spastic diplegic CP. This was a phase I randomized controlled trial with single blinding. The interventions were performed in community-based outpatient physical therapy clinics. Outcome assessments were performed in university laboratories. Sixty-two ambulatory children aged 7 to 18 years with spastic diplegic CP and Gross Motor Function Classification System levels I to III participated in this study. Participants were randomly assigned to cycling or control (no-intervention) groups. Thirty intervention sessions occurred over 12 weeks. Primary outcomes were peak knee extensor and flexor moments, the 600-Yard Walk-Run Test, the Thirty-Second Walk Test, and the Gross Motor Function Measure sections D and E (GMFM-66). Significant baseline-postintervention improvements were found for the 600-Yard Walk-Run Test, the GMFM-66, peak knee extensor moments at 120 degrees /s, and peak knee flexor moments at 30 degrees /s for the cycling group. Improved peak knee flexor moments at 120 degrees/s were found for the control group only, although not all participants could complete this speed of testing. Significant differences between the cycling and control groups based on change scores were not found for any outcomes. Limitations Heterogeneity of the patient population and intrasubject variability were limitations of the study. Significant improvements in locomotor endurance, gross motor function, and some measures of strength were found for the cycling group but not the control group, providing preliminary support for this intervention. As statistical differences were not found in baseline-postintervention change scores between the 2 groups; the results did not demonstrate that stationary cycling was more effective than no intervention. The results of this phase I study provide guidance for future research.

슬관절 등속성 근력에 대한 전통적 굴/신근 비율과 기능적 굴/신근 비율

Purpose: The purpose of this study was to investigate the conventional and functional ratios for isokinetic hamstring: quadriceps strength in college students. Method: The subjects for this study were composed of 31 healthy college students who had no medical history of the lower extremity such as surgery of knee and ankle. The measurement was performed by use of Biodex system 3 model in angular velocity 60, 180°/s and 4 repetitions. Maximal concentric and eccentric quadriceps and hamstring muscle strength was obtained by measuring maximal force moment during isokinetic knee extension and flexion movements. The variables of measure were peak torque % body weight, conventional and functional ratios. Conventional hamstring: quadriceps ratios were calculated as dividing the maximal concentric knee flexor moment by concentric knee extensor moment obtained at a given joint angular velocity. Whereas functional hamstring: quadriceps ratios were calculated as dividing the maximal eccentric knee extensor moment by concentric knee extensor moment obtained at a given joint angular velocity. Result: As this study, it was the higher eccentric hamstring strength than concentric hamstring strength in both male and female. The functional ratios were higher than the conventional ratios. In both male and female, conventional and functional ratios increased as velocity increased. Range of the conventional ratios by concentric contraction(Hamcon/Quadecc) were about 53~55% at 60°/s and 63~64% at 180°/s. However, range of the functional ratios(Hamecc/Quadcon) were 80~88% at 60°/s and 105~115% at 180°/s. There were no significant difference between male and female in both conventional and functional ratios. Conclusion: The agonist-antagonist strength relationship strength for knee extension and flexion may better described by the more functional ratios of eccentric hamstring to concentric quadriceps.

Role of individual lower limb joints in reactive stability control following a novel slip in gait

Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel and unannounced slip during the ensuing single-stance phase. Ten young adults’ resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of support (BOS) (i.e. their state variables, x COM, x ˙ COM , x BOS, x ˙ BOS ), and in the COM stability. The model simulation revealed that these joints had little influence on x ˙ COM but had substantial impact on x ˙ BOS reduction, leading to improve the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar–flexor moments could lead to as much as 57.72±10.46 or 22.33±5.55 and 13.09±2.27 units of reduction in normalized x ˙ BOS , respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability.

A pneumatically powered knee-ankle-foot orthosis (KAFO) with myoelectric activation and inhibition

BackgroundThe goal of this study was to test the mechanical performance of a prototype knee-ankle-foot orthosis (KAFO) powered by artificial pneumatic muscles during human walking. We had previously built a powered ankle-foot orthosis (AFO) and used it effectively in studies on human motor adaptation, locomotion energetics, and gait rehabilitation. Extending the previous AFO to a KAFO presented additional challenges related to the force-length properties of the artificial pneumatic muscles and the presence of multiple antagonistic artificial pneumatic muscle pairs.MethodsThree healthy males were fitted with custom KAFOs equipped with artificial pneumatic muscles to power ankle plantar flexion/dorsiflexion and knee extension/flexion. Subjects walked over ground at 1.25 m/s under four conditions without extensive practice: 1) without wearing the orthosis, 2) wearing the orthosis with artificial muscles turned off, 3) wearing the orthosis activated under direct proportional myoelectric control, and 4) wearing the orthosis activated under proportional myoelectric control with flexor inhibition produced by leg extensor muscle activation. We collected joint kinematics, ground reaction forces, electromyography, and orthosis kinetics.ResultsThe KAFO produced ~22%–33% of the peak knee flexor moment, ~15%–33% of the peak extensor moment, ~42%–46% of the peak plantar flexor moment, and ~83%–129% of the peak dorsiflexor moment during normal walking. With flexor inhibition produced by leg extensor muscle activation, ankle (Pearson r-value = 0.74 ± 0.04) and knee ( r = 0.95 ± 0.04) joint kinematic profiles were more similar to the without orthosis condition compared to when there was no flexor inhibition (r = 0.49 ± 0.13 for ankle, p = 0.05, and r = 0.90 ± 0.03 for knee, p = 0.17).ConclusionThe proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control. The current orthosis design provided knee torques smaller than the ankle torques due to the trade-off in torque and range of motion that occurs with artificial pneumatic muscles. Future KAFO designs could incorporate cams, gears, or different actuators to transmit greater torque to the knee.

Lower extremity walking mechanics of young individuals with asymptomatic varus knee alignment

Varus knee alignment is associated with an increased risk for developing medial knee osteoarthritis (OA). Medial knee OA is commonly associated with altered walking mechanics in the frontal and sagittal planes, as well as altered ground reaction forces. It is unknown whether these mechanics are present in young, asymptomatic individuals with varus knees. We expected that varus-aligned individuals would generally present with frontal plane mechanics that were similar to those reported for individuals with medial knee OA. The gait mechanics of 17 asymptomatic individuals with varus knees and 17 healthy, normally aligned controls were recorded. Gait parameters associated with medial knee OA were compared between groups. The individuals with varus knees exhibited greater knee external adduction moments, knee adduction, eversion, and lateral ground reaction force than the normally aligned individuals. In addition, those with varus knees also demonstrated increased knee flexion and external knee flexor moments during midstance. These results suggest that individuals with varus knees exhibit some, but not all, of the altered mechanics seen in medial knee OA.

Effects of Shock Absorbing Insoles on Knee Pain and Gait in Persons with Knee Osteoarthritis

Osteoarthritis (OA) is a progressive, chronic disease causing pain, limited function,and decreased quality of life. PURPOSE: To investigate the effects of shock absorbing insoles (SAI) on knee pain and lower extremity kinetics in persons with knee OA. METHODS: Sixty community-dwelling seniors (age 63.9 + 8.8 years) with knee OA and knee pain on most days completed a demographic form, Western Ontario and McMaster University Osteoarthritis Index, and three walking tasks with and without a SAI. The walking tasks were: 1) usual pace; 2) fast pace; 3) 6- minute walk test. After each walking task, participants rated their knee pain. Participants also completed a 3-D gait analysis at their usual pace. Separate one-way within subject repeated measures ANOVA's were used to compare outcome variables. RESULTS: Participants reported significantly less pain after walking 6 minutes while wearing the SAI (26 + 25.7 mm) as compared to without the SAI (31.4 + 28 mm, F1,59 = 5.067, p = .028, ES = .079, 1-β=60). No significant differences in knee pain (with or without SAI) were found during the other walking conditions. Gait analysis revealed no significant differences in the time to reach peak vertical ground reaction force (VGRF), peak VGRF, loading rate, peak knee flexor moment or average knee moment between the two conditions. CONCLUSIONS: The use of a SAI in older adults with knee OA decreases knee pain during walking; however, they have no effect on gait mechanics.

Influences of hip external rotation strength on knee mechanics during single-leg drop landings in females

Background To determine the influence of hip external rotation strength on kinematic and kinetic variables during single-leg drop landings. Methods Females were divided into strong and weak groups based on isometric hip external rotation strength and lower extremity flexion–extension and varus–valgus kinematics and kinetics were evaluated during single-legged 40 cm drop landings. Findings Hip external rotation strength had no effect on sagittal or frontal plane angular motion throughout the landing cycle at the hip and knee. The strong group generated a statistically significant decrease in the peak vertical ground reaction force and external knee flexor moment. The weak group produced a greater external knee adduction moment, net knee anterior shear joint reaction force, and a greater hip external adduction moment. Interpretation Subjects with greater hip and quadriceps/hamstring strength exhibited a significant decrease in the vertical ground reaction force and external knee adduction and flexor moments. Hip and knee strength appear to relate to differences in high risk landing strategies.

Influence of additional load on the moments of the agonist and antagonist muscle groups at the knee joint during closed chain exercise

The present study investigated the influence of additional loads on the knee net joint moment, flexor and extensor muscle group moments, and cocontraction index during a closed chain exercise. Loads of 8, 28, or 48 kg (i.e., respectively, 11.1 ± 1.5%, 38.8 ± 5.3%, and 66.4 ± 9.0% of body mass) were added to subjects during dynamic half squats. The flexor and extensor muscular moments and the amount of cocontraction were estimated at the knee joint using an EMG-and-optimization model that includes kinematics, ground reaction, and EMG measurements as inputs. In general, our results showed a significant influence of the Load factor on the net knee joint moment, the extensor muscular moment, and the flexor muscle group moment (all Anova p < .05). Hence we confirmed an increase in muscle moments with increasing load and moreover, we also showed an original “more than proportional” evolution of the flexor and extensor muscle group moments relative to the knee net joint moment. An influence of the Phase (i.e., descent vs. ascent) factor was also seen, revealing different activation strategies from the central nervous system depending on the mode of contraction of the agonist muscle group. The results of the present work could find applications in clinical fields, especially for rehabilitation protocols.

The identification of age-related differences in kinetic gait parameters using principal component analysis

Background. The age of onset of adult-like kinetic gait patterns is controversial. A potential cause of discrepant results between studies is the statistical analyses used to test for differences in kinetic parameters between age groups. Therefore, the purpose of this study was to identify age-related differences in kinetic gait parameters across children aged 3–13 years using principal component analysis. Methods. Principal component analysis was applied to seven kinetic waveform variables ( N = 7) from each of four age groups (3–4 years ( n = 13); 5–6 years ( n = 10); 7–8 years ( n = 12); and 9–13 years ( n = 12)). The principal component scores for each kinetic variable were used to test for group differences using one-way ANOVA and Kruskal–Wallis tests. Findings. Significant group differences ( P < 0.05) were found for five of the principal component scores. Plantarflexion moments increased with age and the oldest group of children (9–13 years old) demonstrated significantly larger plantarflexor moment patterns compared to all other age groups. The 9–13 years old showed significantly larger knee flexor and extensor moments for the first half of the cycle and a later reversal to extensor moments in terminal stance compared to 3–6 years old. The older group also showed decreased hip extensor moments for the first third of the cycle and increased flexor moments in the second third of the cycle compared to the 3–4 and 7–8 years old. Larger stance phase hip abduction moments were observed in the older group compared to all other groups. This was followed by a more complex pattern of alternating moments. Hip power also showed a complex series of differences between age-groups. Interpretation. Compared to parameterization techniques, principal component analysis identified different characteristics in kinetic gait data to discriminate between paediatric age groups. This is the first study to identify age-related differences in gait kinetics using waveform analysis.

The effect of direct measurement versus cadaver estimates of anthropometry in the calculation of joint moments during above-knee prosthetic gait in pediatrics

Joint reaction forces, moments and powers are important in interpreting gait mechanics and compensatory strategies used by patients walking with above-knee prostheses. Segmental anthropometrics, required to calculate joint moments, are often estimated using data from cadaver studies. However, these values may not be accurate for patients following amputation as prostheses are composed of non-biologic material. The purpose of this study was to compare joint moments using anthropometrics calculated from cadaver studies versus direct measurements of the residual limb and prosthesis for children with an above-knee amputation. Gait data were collected for four subjects with above-knee prostheses walking at preferred and fast speeds. Joint moments were computed using anthropometrics from cadaver studies and direct measurements for each subject. The difference between these two methods primarily affected the inertia couple (I α term) and the inertial effect due to gravity, which comprised a greater percentage of the total joint moment during swing as compared to stance. Peak hip and knee flexor and extensor moments during swing were significantly greater when calculated using cadaver data ( p<0.05). These differences were greater while walking fast as compared to slow speeds. A significant difference was not found between these two methods for peak hip and knee moments during stance. A significant difference was found for peak ankle joint moments during stance, but the magnitude was not clinically important. These results support the use of direct measurements of anthropometry when examining above-knee prosthetic gait, particularly during swing.

Albuterol increases lean body mass in ambulatory boys with Duchenne or Becker muscular dystrophy

Albuterol is a beta-2 agonist that has been demonstrated to increase muscle strength in studies in animals and humans. Based on a pilot study of extended-release albuterol Repetabs in children with dystrophinopathies, the authors conducted a randomized, double-blind, placebo-controlled study with a crossover design. Fourteen boys with Duchenne or Becker muscular dystrophy, 6 to 11 years old, completed two treatment periods (albuterol and placebo), 12 weeks each, separated by a 12-week washout period. As the albuterol Repetab formulation was no longer available, an alternate extended release albuterol was used (Volmax, 12 mg per day). Outcome measurements included 1) lean body mass, 2) fat mass, 3) isometric knee extensor and flexor moments, 4) manual muscle testing, and 5) timed functional tests. Lean body mass was significantly higher for subjects following albuterol treatment compared to placebo treatment, while fat mass was significantly lower. No differences were found in isometric knee moments or manual muscle tests. Time to run/walk 30 feet was improved following albuterol. Short-term treatment with extended release albuterol may increase lean body mass, decrease fat mass, and improve functional measures in patients with dystrophinopathies. However, the significant change in strength of specific muscle groups found in the pilot study was not observed in the present study. These findings may be attributed to differences in the drug release and kinetics between Repetab and Volmax formulations as they affect the concentration of available beta-2 receptors on the muscle cell surface differently.

Gait and balance of transfemoral amputees using passive mechanical and microprocessor-controlled prosthetic knees

Background Microprocessor-controlled knee joints appeared on the market a decade ago. These joints are more sophisticated and more expensive than mechanical ones. The literature is contradictory regarding changes in gait and balance when using these sophisticated devices. Methods This study employed a crossover design to assess the comparative performance of a passive mechanical knee prosthesis compared to a microprocessor-controlled knee joint in 15 subjects with an above-knee amputation. Objective measurements of gait and balance were obtained. Results Subjects demonstrated significantly improved gait characteristics after receiving the microprocessor-controlled prosthetic knee joint ( p < 0.01). Improvements in gait were a transition from a hyperextended knee to a flexed knee during loading response which resulted in a change from an internal knee flexor moment to a knee extensor moment. The participants’ balance also improved ( p < 0.01). All conditions of the Sensory Organization Test (SOT) demonstrated improvements in equilibrium score. The composite score also increased. Conclusions Transfemoral amputees using a microprocessor-controlled knee have significant improvements in gait and balance.

Kinematic and Kinetic Outcomes After Identical Multilevel Soft Tissue Surgery in Children With Cerebral Palsy

This study evaluates the outcomes of multilevel soft tissue surgery in 31 ambulatory children (n = 39 sides) with cerebral palsy. All children had undergone rectus femoris transfer, hamstring lengthening, and gastrosoleus lengthening for the purpose of correcting sagittal plane abnormalities. There were no simultaneous bony surgeries. Preoperative and postoperative evaluation consisted of clinical assessment and gait analysis, including 3-dimensional kinematics and kinetics. Results demonstrated improvements in knee and ankle function. At the knee, there was a decrease in mean flexion at initial contact (from 31 degrees [SD, +/-8 degrees] to 21 degrees [SD, +/-10 degrees]) and in stance (mean stance, 22 degrees [SD, +/-12 degrees] to 16 degrees [SD, +/-11 degrees]) associated with a decreased mean internal extensor moment in stance (from 0.09 Nm/kg [SD, +/-0.24 Nm/kg] to -0.03 [SD, +/-0.22 Nm/kg]). At the same time, knee flexion was preserved in swing and occurred earlier. At the ankle, mean dorsiflexion improved at the time of examination (from 8 degrees [SD, +/-9 degrees] to 14 degrees [SD, +/-11 degrees] with the knee in extension), in terminal stance (peak from 7 degrees [SD, +/-9 degrees] to 12 degrees [SD, +/-8 degrees]), and in swing. Peak ankle power generation in stance was preserved and shifted later in stance toward push-off, with no functional weakening of the ankle plantar flexors. A longer-term assessment of a subset of patients with a second postoperative gait analysis at a mean of 4 years after surgery showed that gains measured at 1 year were maintained during the longer term. A subgroup demonstrating a jump knee gait pattern (as defined by excessive knee flexion at initial contact followed by rapid knee extension to full knee extension in midstance) had a tendency to go into knee hyperextension in stance with resultant net knee flexor moment after surgery. This raises concern about the indications for hamstring lengthening in this patient group.