Jill S. Higginson

Differences in gait parameters between healthy subjects and persons with moderate and severe knee osteoarthritis: A result of altered walking speed?

BACKGROUND While knee osteoarthritis has been shown to affect a multitude of kinematic, kinetic and temporo-spatial gait parameters, few investigations have examined the effect of increasing levels of radiographic osteoarthritis severity on these gait parameters. Fewer still have investigated the effect of walking speed on gait variables in persons with knee osteoarthritis. The objective of this study was to investigate the influence of walking speed on biomechanical variables associated with joint loading in persons with varying severities of medial compartment knee osteoarthritis. METHODS Twenty-one persons with moderate osteoarthritis (Kellgren-Lawrence score 2-3) and 13 persons with severe osteoarthritis (Kellgren-Lawrence score of 4) participated. Twenty-two persons without knee pain or radiographic evidence of arthritis comprised a healthy control group. Sagittal plane kinetics, knee adduction moment, sagittal plane knee excursion, ground reaction forces and knee joint reaction forces were calculated from three-dimensional motion analysis at 1.0m/s, self-selected and fastest tolerable walking speeds. Differences were analyzed using multivariate analysis of variance and multivariate analysis of covariance with speed as a covariate. FINDINGS Persons with knee osteoarthritis showed significantly lower knee and ankle joint moments, ground reaction forces, knee reaction force and knee excursion when walking at freely chosen speeds. When differences in walking speed were accounted for in the analysis, the only difference found at all conditions was decreased knee joint excursion. INTERPRETATION Compared to a healthy control group, persons with knee OA demonstrate differences in joint kinetics and kinematics. Except for knee excursion, these differences in gait parameters appear to be a result of slower freely chosen walking speeds rather than a result of disease progression.

Functional Electrical Stimulation of Ankle Plantarflexor and Dorsiflexor Muscles. Effects on Poststroke Gait

Background and Purpose— Functional electrical stimulation (FES) is a popular poststroke gait rehabilitation intervention. Although stroke causes multijoint gait deficits, FES is commonly used only for the correction of swing-phase foot drop. Ankle plantarflexor muscles play an important role during gait. The aim of the current study was to test the immediate effects of delivering FES to both ankle plantarflexors and dorsiflexors on poststroke gait. Methods— Gait analysis was performed as subjects (N=13) with chronic poststroke hemiparesis walked at their self-selected walking speeds during walking with and without FES. Results— Compared with delivering FES to only the ankle dorsiflexor muscles during the swing phase, delivering FES to both the paretic ankle plantarflexors during terminal stance and dorsiflexors during the swing phase provided the advantage of greater swing-phase knee flexion, greater ankle plantarflexion angle at toe-off, and greater forward propulsion. Although FES of both the dorsiflexor and plantarflexor muscles improved swing-phase ankle dorsiflexion compared with noFES, the improvement was less than that observed by stimulating the dorsiflexors alone, suggesting the need to further optimize stimulation parameters and timing for the dorsiflexor muscles during gait. Conclusions— In contrast to the typical FES approach of stimulating ankle dorsiflexor muscles only during the swing phase, delivering FES to both the plantarflexor and dorsiflexor muscles can help to correct poststroke gait deficits at multiple joints (ankle and knee) during both the swing and stance phases of gait. Our study shows the feasibility and advantages of stimulating the ankle plantarflexors during FES for poststroke gait.

Novel Patterns of Functional Electrical Stimulation Have an Immediate Effect on Dorsiflexor Muscle Function During Gait for People Poststroke

Background Foot drop is a common gait impairment after stroke. Functional electrical stimulation (FES) of the ankle dorsiflexor muscles during the swing phase of gait can help correct foot drop. Compared with constant-frequency trains (CFTs), which typically are used during FES, novel stimulation patterns called variable-frequency trains (VFTs) have been shown to enhance isometric and nonisometric muscle performance. However, VFTs have never been used for FES during gait. Objective The purpose of this study was to compare knee and ankle kinematics during the swing phase of gait when FES was delivered to the ankle dorsiflexor muscles using VFTs versus CFTs. Design A repeated-measures design was used in this study. Participants Thirteen individuals with hemiparesis following stroke (9 men, 4 women; age=46–72 years) participated in the study. Methods Participants completed 20- to 40-second bouts of walking at their self-selected walking speeds. Three walking conditions were compared: walking without FES, walking with dorsiflexor muscle FES using CFTs, and walking with dorsiflexor FES using VFTs. Results Functional electrical stimulation using both CFTs and VFTs improved ankle dorsiflexion angles during the swing phase of gait compared with walking without FES (X̅±SE=−2.9°±1.2°). Greater ankle dorsiflexion in the swing phase was generated during walking with FES using VFTs (X̅±SE=2.1°±1.5°) versus CFTs (X̅±SE=0.3±1.3°). Surprisingly, dorsiflexor FES resulted in reduced knee flexion during the swing phase and reduced ankle plantar flexion at toe-off. Conclusions The findings suggest that novel FES systems capable of delivering VFTs during gait can produce enhanced correction of foot drop compared with traditional FES systems that deliver CFTs. The results also suggest that the timing of delivery of FES during gait is critical and merits further investigation.

A bilateral comparison of posterior capsule thickness and its correlation with glenohumeral range of motion and scapular upward rotation in collegiate baseball players

HYPOTHESIS We hypothesized that posterior capsule thickness (PCT) would be greater on the dominant arm compared to the non-dominant arm. We also hypothesized that PCT would negatively correlate with glenohumeral internal rotation and scapular upward rotation. In addition, PCT would positively correlate with glenohumeral external rotation. However, currently PCT has not been measured nor have correlations been identified to exist with glenohumeral and scapular motion. Therefore, the purpose of the study was to determine if the posterior capsule was hypertrophied on the dominant arm and to identify if relationships exist with glenohumeral internal rotation (IR), external rotation (ER), and scapular upward rotation (SUR). MATERIALS AND METHODS PCT was measured using a 10-MHz transducer. Glenohumeral IR and ER was measured supine using a digital inclinometer. SUR was measure at 0°, 60°, 90°, and 120° of glenohumeral abduction using a modified digital inclinometer. RESULTS PCT was greater on the dominant compared with the nondominant arm (P = .001). A negative correlation was found between PCT and IR (-0.498, P = .0001). A positive correlation was found between PCT and ER (0.450, P = .002) and between PCT and SUR at 60°, 90°, and 120° of glenohumeral abduction (0.388, P = .006; 0.327, P = .023; 0.304, P = .036, respectively). DISCUSSION This in vivo study demonstrated a hypertrophied posterior capsule and its association with GIRD, ER, and SUR. These observations suggest that PCT does occur on the throwing arm of baseball players and is linked with glenohumeral and scapular alterations. CONCLUSIONS This methodology could be used as a noninvasive screening evaluation for overhead athletes to identify those who may be at risk for shoulder injuries due to excessive capsular thickening.

Alterations in quadriceps and hamstrings coordination in persons with medial compartment knee osteoarthritis.

Altered muscle coordination strategies in persons with knee osteoarthritis (OA) result in an increase in co-contraction of the quadriceps and hamstrings during walking. While this may increase intersegmental joint contact force and expedite disease progression, it is not currently known whether the magnitude of co-contraction increases with a progressive loss of joint space or whether the level of co-contraction is dependent on walking speed. The purposes of this study were to (1) determine if co-contraction increased with OA severity and (2) discern whether differences in co-contraction were a result of altered freely chosen walking speeds or rather an inherent change associated with disease progression. Forty-two subjects with and without knee osteoarthritis were included in the study. Subjects were divided into groups based on disease severity. When walking at a controlled speed of 1.0m/s, subjects with moderate and severe knee OA showed significantly higher co-contraction when compared to a healthy control group. At freely chosen walking speeds only the moderate OA group had significantly higher co-contraction values. Increased walking speed also resulted in a significant increase in co-contraction, regardless of group. The results of this study demonstrate that persons with knee OA develop higher antagonistic muscle activity. This occurs despite differences in freely chosen walking speed. Although subjects with OA had higher co-contraction than the control group, co-contraction may not increase with disease severity.

Gait parameters and stride-to-stride variability during familiarization to walking on a split-belt treadmill

BACKGROUND Subjects unfamiliar to walking on a split-belt treadmill may initially demonstrate an altered gait pattern or increased variability of gait parameters. While previous investigations have examined kinematic variables associated with familiarization time, the objective of this study was to determine the familiarization period required to obtain the most reproducible gait pattern through the assessment of kinetic, kinematic and spatio-temporal parameters during a single session of treadmill walking. METHODS Eleven healthy subjects participated in a single bout of treadmill walking which lasted 9 min. Kinematic and kinetic data were collected from the first 30s of each minute, beginning when the treadmill reached full speed. Means and standard deviations for knee flexion at heel strike, ground reaction forces, step width and step length were obtained to examine the changes in each variable over the 9 min. Mean r(2) values were evaluated for changes in variability from one stride to the subsequent stride for sagittal plane hip, knee and ankle joint angles and moments, as well as for vertical and horizontal ground reaction forces. FINDINGS Significant reductions in variability were found for vertical and horizontal ground reaction forces, knee flexion at heel strike and step length over 9 min. Only step width showed a change in the mean value across trials. There were no increases in r(2) values after the 5th min for any of the gait variables. INTERPRETATION The results suggest that in order to collect accurate data for gait analysis, subjects should be familiarized to the split-belt treadmill for at least 5 min prior to data collection.

Side-to-side differences in overuse running injury susceptibility: A retrospective study

Despite the number of studies examining factors associated with overuse running injury, little is known about why an individual gets injured on a particular side of the body. Abnormal levels of several strength, structural, kinetic, and kinematic factors have been attributed to injury susceptibility. However, while most studies have compared the injured limb of injured runners to an arbitrary limb of healthy controls, there is some evidence to suggest that injury risk is related to characteristics on both sides of a runner. Therefore, the purpose of this study was to investigate how bilateral characteristics of strength, structural, kinetic, and kinematic factors relate to overuse injury. The first purpose was to compare these factors between the injured and uninjured limbs of runners with a history of injury on only one side of their bodies. The results showed that hip internal rotation range of motion and peak tibial acceleration were both elevated on the side with a history of injury. The second purpose was to compare asymmetry levels between the injured runners and runners who had never sustained a running-related injury. Asymmetry levels were similar between groups for all variables, which suggests that some level of asymmetry is normal. The final purpose of the study was to compare bilateral values of these factors between the injured and uninjured runners. The results showed that hip internal rotation range of motion, as well as the deviation from normal arch height index, were bilaterally elevated in the injured runners. Although peak tibial acceleration was different between sides of the injured runners, it was not bilaterally elevated compared to the uninjured runners. These results support the notion that injury risk may be related to risk factors on both sides.

Combined effects of fast treadmill walking and functional electrical stimulation on post-stroke gait.

Gait dysfunctions are highly prevalent in individuals post-stroke and affect multiple lower extremity joints. Recent evidence suggests that treadmill walking at faster than self-selected speeds can help improve post-stroke gait impairments. Also, the combination of functional electrical stimulation (FES) and treadmill training has emerged as a promising post-stroke gait rehabilitation intervention. However, the differential effects of combining FES with treadmill walking at the fast versus a slower, self-selected speed have not been compared previously. In this study, we compared the immediate effects on gait while post-stroke individuals walked on a treadmill at their self-selected speed without FES (SS), at the SS speed with FES (SS-FES), at the fastest speed they are capable of attaining (FAST), and at the FAST speed with FES (FAST-FES). During SS-FES and FAST-FES, FES was delivered to paretic ankle plantarflexors during terminal stance and to paretic dorsiflexors during swing phase. Our results showed improvements in peak anterior ground reaction force (AGRF) and trailing limb angle during walking at FAST versus SS. FAST-FES versus SS-FES resulted in greater peak AGRF, trailing limb angle, and swing phase knee flexion. FAST-FES resulted in further increase in peak AGRF compared to FAST. We posit that the enhancement of multiple aspects of post-stroke gait during FAST-FES suggest that FAST-FES may have potential as a post-stroke gait rehabilitation intervention.

Knee contact force in subjects with symmetrical OA grades: differences between OA severities.

In using musculoskeletal models, researchers can calculate muscle forces, and subsequently joint contact forces, providing insight into joint loading and the progression of such diseases as osteoarthritis (OA). The purpose of this study was to estimate the knee contact force (KCF) in patients with varying degrees of OA severity using muscle forces and joint reaction forces derived from OpenSim. Walking data was obtained from healthy individuals (n=14) and those with moderate (n=10) and severe knee OA (n=2). For each subject, we generated 3D, muscle-actuated, forward dynamic simulations of the walking trials. Muscle forces that reproduced each subjects gait were calculated. KCFs were then calculated using the vector sum of the muscle forces and joint reaction forces along the longitudinal axis of the femur. Moderate OA subjects exhibited a similar KCF pattern to healthy subjects, with lower second peaks (p=0.021). Although subjects with severe OA had similar initial peak KCF to healthy and moderate OA subjects (more than 4 times BW), the pattern of the KCF was very different between groups. After an initial peak, subjects with severe OA continually unloaded the joint, whereas healthy and moderate OA subjects reloaded the knee during late stance. In subjects with symmetric OA grades, there appears to be differences in loading between OA severities. Similar initial peaks of KCF imply that reduction of peak KCF may not be a compensatory strategy for OA patients; however, reducing duration of high magnitude loads may be employed.

Dynamic knee joint stiffness in subjects with a progressive increase in severity of knee osteoarthritis

BACKGROUND Persons with knee osteoarthritis demonstrate a reduction in knee joint excursion during loading response which is often coupled with a reduction in the moment acting to flex the knee. While these individual kinetic and kinematic changes are well documented, the interaction between changes in joint moment and changes in joint angle (dynamic joint stiffness) is not well understood in persons with knee osteoarthritis. METHODS Twelve persons with severe knee osteoarthritis (Kellgren-Lawrence score 4) and 22 persons with moderate knee osteoarthritis (Kellgren-Lawrence scores 2-3) were compared to a healthy control group (n=22). Dynamic knee joint stiffness was calculated during loading response and was defined as the slope of the linear regression when joint moment is plotted against joint angle. Group differences were compared at 1.0m/s, self-selected and fast walking speeds using a one-way ANOVA, as well as a one-way ANCOVA to account for differences in freely chosen walking speed. Differences between speeds were compared using an ANOVA with one repeated measure (walking speed). FINDINGS At all walking speeds, the severe group had significantly higher stiffness, even when accounting for differences in walking speed (P0.038). A significant increase in dynamic joint stiffness was found for all groups when speed was increased (P=0.001). INTERPRETATION Persons with advanced stages of knee osteoarthritis develop higher joint stiffness irrespective of walking speed. While this may be a strategy to overcome knee instability often reported in this population during walking, the potential detrimental effects of higher dynamic joint stiffness should be explored in future research.