J. Harlaar

Varus-valgus motion and functional ability in patients with knee osteoarthritis

Objective: To assess the relationship between knee varus–valgus motion and functional ability, and the impact of knee varus–valgus motion on the relationship between muscle strength and functional ability in patients with osteoarthritis (OA) of the knee. Methods: Sixty-three patients with knee OA were tested. Varus–valgus motion was assessed by optoelectronic recording and three-dimensional motion analysis. Functional ability was assessed by observation, using a 100 m walking test, a Get Up and Go test, and WOMAC questionnaire. Muscle strength was measured by a computer-driven isokinetic dynamometer. Regression analyses were performed to assess the relationships between varus–valgus motion and functional ability, and to assess the impact of varus–valgus motion on the relationship between muscle strength and functional ability. Results: In patients with high varus–valgus range of motion, muscle weakness was associated with a stronger reduction in functional ability (ie, longer walking time and Get Up and Go time) than in patients with low varus–valgus range of motion. A pronounced varus position and a difference between the left and right knees in varus–valgus position were related with reduced functional ability. Conclusions: In patients with knee OA with high varus–valgus range of motion, muscle weakness has a stronger impact on functional ability than in patients with low varus–valgus range of motion. Patients with knee OA with more pronounced varus knees during walking show a stronger reduction in functional ability than patients with less pronounced varus knees or with valgus knees.

Dynamic spasticity of plantar flexor muscles in cerebral palsy gait

OBJECTIVEnTo quantify dynamic spasticity, i.e. the coupling between muscle-tendon stretch velocity and muscle activity during gait, of the gastrocnemius and soleus muscles in children with spastic cerebral palsy.nnnDESIGNnProspective, cross-sectional study.nnnSUBJECTSnSeventeen ambulatory children with cerebral palsy with spastic calf muscles, and 11 matched typically developing children.nnnMETHODSnThe children walked at 3 different speeds. Three-dimensional kinematic and electromyographic data were collected. Muscle-tendon velocities of the gastrocnemius medialis and soleus were calculated using musculoskeletal modelling.nnnRESULTSnIn typically developing children, muscles were stretched fast in swing without subsequent muscle activity, while spastic muscles were stretched more slowly for the same walking speed, followed by an increase in muscle activity. The mean ratio between peak activity and peak stretch velocity in swing was approximately 4 times higher in spastic muscles, and increased with walking speed. In stance, the stretch of muscles in typically developing children was followed by an increase in muscle activity. Spastic muscles were stretched fast in loading response, but since muscle activity was already built up in swing, no clear dynamic spasticity effect was present.nnnCONCLUSIONnSpastic calf muscles showed increased coupling between muscle-tendon stretch velocity and muscle activity, especially during the swing phase of gait.

Effect of selective dorsal rhizotomy on gait in children with bilateral spastic paresis: kinematic and EMG-pattern changes.

INTRODUCTIONnSelective dorsal rhizotomy (SDR) is an effective treatment for reducing spasticity and improving gait in children with spastic cerebral palsy. Data concerning muscle activity changes after SDR treatment are limited.nnnPATIENTS AND METHODSnIn 30 children who underwent SDR a gait analysis was performed before and 12-24 months postoperatively. Subjects walked on a 10-m walkway at comfortable walking speed. Biplanar video was registered and surface EMG was recorded. Sagittal knee angles were measured from video and observational gait assessments were performed using the Edinburgh gait assessment scale (EGAS).nnnRESULTSnThe EGAS significantly improved after SDR (p<0.001). There were significant improvements of the knee angle kinematics (p<0.001). Only slight changes in EMG activity were observed. The activity of the m. gastrocnemius (GM) decreased and a late peak appeared in stance, the activity of the m. semitendinosus (ST) increased in stance. The activity of the m. rectus femoris (RF) decreased in swing.nnnCONCLUSIONnSDR improved overall gait performance but EMG changes were only slight. Better timing of the GM in stance and reduced activity of RF in swing may have increased knee flexion in swing. Reduced hamstrings spasticity may have led to postural instability in the hip.

Effect of real-time biofeedback on peak knee adduction moment in patients with medial knee osteoarthritis: Is direct feedback effective?

Background: Gait modifications can reduce the knee adduction moment, a representation of knee loading. Reduced loading may help to slow progression of medial knee osteoarthritis. We aimed to investigate the response of patients with medial knee osteoarthritis to direct feedback on the knee adduction moment as a method for modifying the gait pattern, before and after training with specific gait modifications. Methods: Forty patients with medial knee osteoarthritis underwent 3D gait analysis on an instrumented‐treadmill, while receiving real‐time feedback on the peak knee adduction moment. Patients were trained with three different modifications; toe‐in, wider steps and medial thrust gait. The response to real‐time feedback on the knee adduction moment was measured before and after training. To evaluate the short term retention effect, we measured the changes without feedback. We also evaluated the effects on the knee flexion moment and at the hip and ankle joints. Findings: With direct feedback on the knee adduction moment, patients were initially unable to reduce the knee adduction moment. After training with specific modifications, peak knee adduction moment was reduced by 14% in response to direct feedback. Without feedback a 9% reduction in peak knee adduction moment was maintained. Hip moments were not increased with modified gait, but small increases in ankle adduction moment and knee flexion moment were observed. Interpretation: Real‐time biofeedback directly on the knee adduction moment is a promising option for encouraging gait modifications to reduce knee loading, however only when combined with specific instructions on how to modify the gait. HIGHLIGHTSWith direct feedback on knee adduction moment alone, patients were unable to significantly reduce the knee adduction moment.When provided with specific instructions and direct feedback, significant reductions were found.Reductions in knee adduction moment were maintained after removal of the feedback.

Inertial sensing in a hand held dynamometer

Two methods for kinematic sensing in a hand-held dynamometer using accelerometers and gyroscopes are presented. The first method integrates the angular velocity signal from the gyroscope, after calibration of gyroscope offset and joint angle from a static period immediately preceding each measurement. The second method estimates tangential and radial accelerations, enabling the estimation of the gravity components in the accelerometer signals under dynamic conditions, and thus angle reconstruction. The second method appeared to perform best in preliminary tests.

The learning process of gait retraining using real-time feedback in patients with medial knee osteoarthritis

The objective of this study was to investigate the learning process of knee osteoarthritis (KOA) patients learning to change their foot progression angle (FPA) over a six-week toe-in gait training program. Sixteen patients with medial KOA completed a six-week toe-in gait training program with real-time biofeedback. Patients walked on an instrumented treadmill while receiving real-time feedback on their foot progression angle (FPA) with reference to a target angle. The FPA difference (difference between target and actual FPA) was analyzed during i) natural walking, ii) walking with feedback, iii) walking without feedback and iv) walking with a dual-task at the start and end of the training program. Self-reported difficulty and abnormality and time spent walking and training were also analyzed. The FPA difference during natural walking was significantly decreased from median 6.9 to median 3.6° i.e. by 3.3° in week six (pu202f<u202f0.001); adding feedback reduced FPA difference to almost zero. However the dual-task condition increased the FPA difference at week one compared to the feedback condition (median difference: 1.8°, pu202f=u202f0.022), but after training this effect was minimized (median difference: 0.6°, pu202f=u202f0.167). Self-reported abnormality and difficulty decreased from median 5 to 3 and from median 6 to 3 on the NRS respectively (pu202f<u202f0.05). Patients with medial KOA could reduce the FPA difference during natural walking after the gait retraining program, with some evidence of a reduction in the cognitive demand needed to achieve this. Automation of adaptions might need support from more permanent feedback using wearable technologies.

The immediate effect of a soft knee brace on pain, activity limitations, self-reported knee instability, and self-reported knee confidence in patients with knee osteoarthritis

BackgroundWe aimed to (i) evaluate the immediate effect of a soft knee brace on pain, activity limitations, self-reported knee instability, and self-reported knee confidence, and (ii) to assess the difference in effect between a non-tight and a tight soft brace in patients with knee osteoarthritis (OA).MethodsForty-four patients with knee OA and self-reported knee instability participated in the single-session, laboratory, experimental study. A within-subject design was used, comparing a soft brace with no brace, and comparing a non-tight with a tight soft brace. The outcome measures were pain, self-reported knee instability and knee confidence during level and perturbed walking on the treadmill and activity limitations (10-m walk test and the get up and go (GUG) test). Linear mixed-effect model analysis for continuous outcomes and logistic generalized estimating equations for categorical outcomes were used to evaluate the effect of wearing a soft brace.ResultsWearing a soft brace significantly reduced pain during level walking (Bu2009−u20090.60, Pu2009=u20090.001) and perturbed walking (Bu2009−u20090.80, Pu2009<u20090.001), reduced the time to complete the 10-m walk (Bu2009−u20090.23, Pu2009<u20090.001) and the GUG tests (Bu2009−u20090.23, Pu2009=u20090.004), reduced self-reported knee instability during level walking (OR 0.41, Pu2009=u20090.002) and perturbed walking (OR 0.36, Pu2009<u20090.001), and reduced lack of confidence in the kneesxa0during level walking (OR 0.45, Pu2009<u20090.001) and perturbed walking (OR 0.56, Pu2009<u20090.001), compared with not wearing a soft brace. There was no difference in effects between a non-tight and tight brace, except for the 10-m walk test. Wearing a tight brace significantly reduced the time to complete the 10-m walk test in comparison with wearing a non-tight brace (Bu2009−u20090.11, Pu2009=u20090.03).ConclusionThe results of this study indicate that a soft brace is an efficacious intervention targeting pain, activity limitations, self-reported knee instability, and knee confidence in the immediate term in patients with knee OA. Further studies are needed evaluating the mode of action based on exerted pressure, and on the generalization to functioning in daily life.Trial registrationtrialregister.nl, NTR6363. Retrospectively registered on 15 May 2017.

The immediate effect of a soft knee brace on dynamic knee instability in persons with knee osteoarthritis

ObjectivesnWearing a soft knee brace has been shown to reduce self-reported knee instability in persons with knee OA. There is a need to assess whether a soft knee brace has a beneficial effect on objectively assessed dynamic knee instability as well. The aims of the study were to evaluate the effect of a soft knee brace on objectively assessed dynamic knee instability and to assess the difference in effect between a non-tight and a tight soft knee brace in persons with knee OA.nnnMethodsnThirty-eight persons with knee OA and self-reported knee instability participated in a laboratory study. A within-subject design was used comparing no brace vs brace and comparing a non-tight vs a tight brace. The primary outcome measure was dynamic knee instability, expressed by the perturbation response (PR). The PR reflects deviation in the mean knee varus-valgus angle during level walking after a controlled mechanical perturbation. Linear mixed-effect model analysis was used to evaluate the effect of a brace on dynamic knee instability.nnnResultsnWearing a brace significantly reduced the PR compared with not wearing a brace (B = -0.16, P = 0.01). There was no difference between a non-tight and a tight brace (B = -0.03, P = 0.60).nnnConclusionnThis study is the first to report that wearing a soft knee brace reduces objectively assessed dynamic knee instability in persons with knee OA. Wearing a soft brace results in an objective improvement of knee instability beyond subjectively reported improvement.nnnTrial registrationnNederlands Trial register (trialregister.nl) NTR6363.

Relationship between knee joint contact forces and external knee joint moments in patients with medial knee osteoarthritis: effects of gait modifications

OBJECTIVEnTo evaluate 1) the relationship between the knee contact force (KCF) and knee adduction and flexion moments (KAM and KFM) during normal gait in people with medial knee osteoarthritis (KOA), 2) the effects on the KCF of walking with a modified gait pattern and 3) the relationship between changes in the KCF and changes in the knee moments.nnnMETHODnWe modeled the gait biomechanics of thirty-five patients with medial KOA using the AnyBody Modeling System during normal gait and two modified gait patterns. We calculated the internal KCF and evaluated the external joint moments (KAM and KFM) against it using linear regression analyses.nnnRESULTSnFirst peak medial KCF was associated with first peak KAM (R2xa0=xa00.60) and with KAM and KFM (R2xa0=xa00.73). Walking with both modified gait patterns reduced KAM (Pxa0=xa00.002) and the medial to total KCF ratio (Pxa0<xa00.001) at the first peak. Changes in KAM during modified gait were moderately associated with changes in the medial KCF at the first peak (R2xa0=xa00.54 and 0.53).nnnCONCLUSIONSnAt the first peak, KAM is a reasonable substitute for the medial contact force, but not at the second peak. First peak KFM is also a significant contributor to the medial KCF. At the first peak, walking with a modified gait reduced the ratio of the medial to total KCF but not the medial KCF itself. To determine the effects of gait modifications on cartilage loading and disease progression, longitudinal studies and individualized modeling, accounting for motion control, would be required.

Gait retraining using real-time feedback in patients with medial knee osteoarthritis: Feasibility and effects of a six-week gait training program

BACKGROUNDnThe knee adduction moment (KAM) is often elevated in medial knee osteoarthritis (KOA). The aim of this study was to evaluate effects on KAM and patient-reported outcomes of a six-week gait training program.nnnMETHODSnTwenty-one patients (61u202f±u202f6 years) with KOA participated in a six-week biofeedback training program to encourage increased toe-in (all patients) and increased step-width (five patients). Patients received real-time visual feedback while walking on an instrumented treadmill. We analysed the effect of the gait modification(s) on peak KAM in week six and three and six months post-training. We also evaluated the effect on pain and functional ability.nnnRESULTSnOf 21 patients starting the program, 16 completed it with high attendance (15 and 16 respectively) at the three and six month follow-ups. First peak KAM was significantly reduced by up to 14.0% in week six with non-significant reductions of 8.2% and 5.5% at the follow-ups. Functional ability (assessed using the WOMAC questionnaire) improved significantly after the training (eight point reduction, pu202f=u202f0.04 in week six and nine point reduction, pu202f=u202f0.04 at six-month follow-up). There was also a trend towards reduction in WOMAC pain (pu202f=u202f0.06) at follow-up.nnnCONCLUSIONSnBiofeedback training to encourage gait modifications is feasible and leads to short-term benefits. However, at follow-up, reductions in KAM were less pronounced in some participants suggesting that to influence progression of KOA in the longer term, a permanent regime to reinforce the effects of the training program is needed. Trial number: ISRCTN14687588.