J.R. Giffin

Lateral trunk lean explains variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis

OBJECTIVE To test the hypothesis that selected gait kinematics, particularly lateral trunk lean, observed in patients with medial compartment knee osteoarthritis explain variation in dynamic knee joint load. METHOD In this cross-sectional observational study, 120 patients with radiographically confirmed varus gonarthrosis underwent three-dimensional gait analysis at their typical walking speed. We used sequential (hierarchical) linear regression to examine the amount of variance in dynamic knee joint load (external knee adduction moment) explained by static lower limb alignment (mechanical axis angle) and gait kinematics determined a priori based on their proposed effect on knee load (walking speed, toe-out angle, and lateral trunk lean angle). RESULTS Approximately 50% of the variation in the first peak external knee adduction moment was explained by mechanical axis angle (25%), Western Ontario and McMaster Universities Osteoarthritis Index pain score (1%), gait speed (1%), toe-out angle (12%), and lateral trunk lean angle (13%). There was no confounding or interaction with Kellgren and Lawrence grade of severity. CONCLUSIONS Gait kinematics, particularly lateral trunk lean, explain substantial variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis. While largely ignored in previous gait studies, the effect of lateral trunk lean should be considered in future research evaluating risk factors and interventions for progression of knee osteoarthritis.

Biomechanical effects of valgus knee bracing: a systematic review and meta-analysis

To review and synthesize the biomechanical effects of valgus knee bracing for patients with medial knee osteoarthritis (OA). Electronic databases were searched from their inception to May 2014. Two reviewers independently determined study eligibility, rated study quality and extracted data. Where possible, data were combined into meta-analyses and pooled estimates with 95% confidence intervals (CI) for standardized mean differences (SMD) were calculated. Thirty studies were included with 478 subjects tested while using a valgus knee brace. Various biomechanical methods suggested valgus braces can decrease direct measures of medial knee compressive force, indirect measures representing the mediolateral distribution of load across the knee, quadriceps/hamstring and quadriceps/gastrocnemius co-contraction ratios, and increase medial joint space during gait. Meta-analysis from 17 studies suggested a statistically significant decrease in the external knee adduction moment (KAM) during walking, with a moderate-to-high effect size (SMD = 0.61; 95% CI: 0.39, 0.83; P < 0.001). Meta-regression identified a near-significant association for the KAM effect size and duration of brace use only (β, -0.01; 95% CI: -0.03, 0.0001; P = 0.06); with longer durations of brace use associated with smaller treatment effects. Minor complications were commonly reported during brace use and included slipping, discomfort and poor fit, blisters and skin irritation. Systematic review and meta-analysis suggests valgus knee braces can alter knee joint loads through a combination of mechanisms, with moderate-to-high effect sizes in biomechanical outcomes.

A comparison of subtalar joint motion during anticipated medial cutting turns and level walking using a multi-segment foot model

The weight-bearing in-vivo kinematics and kinetics of the talocrural joint, subtalar joint and joints of the foot were quantified using optical motion analysis. Twelve healthy subjects were studied during level walking and anticipated medial turns at self-selected pace. A multi-segment model of the foot using skin-mounted marker triads tracked four foot segments: the hindfoot, midfoot, lateral and medial forefoot. The lower leg and thigh were also tracked. Motion between each of the segments could occur in three degrees of rotational freedom, but only six inter-segmental motions were reported in this study: (1) talocrural dorsi-plantar-flexion, (2) subtalar inversion-eversion, (3) frontal plane hindfoot motion, (4) transverse plane hindfoot motion, (5) forefoot supination-pronation twisting and (6) the height-to-length ratio of the medial longitudinal arch. The motion at the subtalar joint during stance phase of walking (eversion then inversion) was reversed during a turning task (inversion then eversion). The external subtalar joint moment was also changed from a moderate eversion moment during walking to a larger inversion moment during the turn. The kinematics of the talocrural joint and the joints of the foot were similar between these two tasks. During a medial turn, the subtalar joint may act to maintain the motions in the foot and talocrural joint that occur during level walking. This is occurring despite the conspicuously different trajectory of the centre of mass of the body. This may allow the foot complex to maintain its function of energy absorption followed by energy return during stance phase that is best suited to level walking.

191 COMBINED EFFECTS OF A VALGUS KNEE BRACE AND LATERAL WEDGE ORTHOTIC ON DYNAMIC KNEE JOINT LOADING IN PATIENTS WITH MEDIAL COMPARTMENT KNEE OSTEOARTHRITIS

Purpose: A number of conservative strategies are suggested to modify the external knee adduction moment and potentially decrease the rate of disease progression for patients with medial compartment knee osteoarthritis (OA). The aim of this study was to compare the effects of a custom-fit knee brace and foot orthotic, when used separately and together, on frontal plane lever arm and external adduction moment about the knee in patients with knee OA.

182 THE EFFECTS OF CHANGES IN BODY COMPOSITION ON DYNAMIC KNEE JOINT LOADING

Methods: Twelve subjects with a traumatic-onset meniscal tear were recruited for this study (11 males; mean age: 19.5±3.0 yrs; 10 lateral tears/2 medial tears). Testing consisted of gait analysis and questionnaires. Retro-reflective markers were placed prior to five walking trials at a self-selected speed. Marker position was recorded with a motion capture system (Motion Analysis Corp), and ground reaction forces were recorded with two force platforms (Advanced Mechanical Technology Inc). The stance phase was analyzed bilaterally, and the variables were sagittal plane knee angle excursion during weight acceptance and from the end of weight-acceptance to midstance, and peak vertical ground reaction force (PVGRF) at heel strike and toe-off. Subjects self-reported knee pain intensity on the 11-point (0–10) numeric rating scale (NRS), fear of movement/re-injury on the shortened Tampa Scale for Kinesophobia (TSK-11), and pain catastrophizing on the Pain Catastrophizing Scale (PCS). Knee angle excursions and PVGRFs were compared between sides with paired t-tests. If a significant difference was found, the magnitude of asymmetry was computed (knee angle excursion: uninjured side-injured side; PVGRF (injured side/uninjured side) *100]. Pearson’s Product Moment correlation determined the association between gait asymmetry and questionnaire scores. Results: Gait variables and questionnaire scores are reported in the Table. Knee angle excursion during weight acceptance and from weight acceptance to mid-stance was reduced on the injured side compared to the uninjured side (p = 0.009 and p =.023, respectively). PVGRF at heel strike and toe-off was not significantly different between sides (p = 0.794 and p=0.869). The asymmetry in knee angle excursion during weight acceptance was negatively correlated with NRS score (r = −0.580, p = 0.048). The asymmetry in knee angle excursion from weight acceptance to midstance was negatively correlated with TSK-11 score (r = −0.833, p = 0.001). Conclusions: Knee angle excursion on the injured side was reduced during the stance phase of gait in people with traumatic meniscal tear. During weight acceptance, knee pain intensity increased as the magnitude of asymmetry decreased; and from the end of weight acceptance until midstance, fear of movement/re-injury increased as the magnitude of asymmetry decreased. Thus, subjects with greater knee motion on the injured side displayed elevated pain and fear of movement/re-injury. These data indicate a potential link between biomechanical measures and relevant psychosocial factors from the fearavoidance model. Although mean PVGRF was not significantly different between sides, asymmetry was as high as 12% (either underor overloading on the injured side) for some subjects.

137 INTERACTION BETWEEN MASS AND ALIGNMENT ON KNEE ADDUCTION MOMENT IN PATIENTS WITH KNEE OSTEOARTHRITIS

creased lower extremity joint excursions and increased muscle co-contraction (CC). Although this stiffened pattern of movement may affect joint loading and disease progression, there is limited information on how this pattern relates to physical function. We examined the association between lower extremity joint excursion and muscle pairs CC with physical function in people with KOA during gait and step down. Methods: Subjects with KOA over the age of 40 participated (n=65). Severity of symptoms determined the Most and LeastAffected (MA and LA) leg. Physical function was measured by a performance based (Get up and Go test) and a self-reported method (WOMAC). Principal component analysis combined these two measures into one component measure of physical function (CPF)-higher scores indicate worse function. Motion analysis and electromyography were performed during gait and step down for both legs. Hip, knee and ankle joint excursions of MA and LA legs were calculated during the loading phase of gait and of step down. Mean CC of the following 5 muscle pairs were computed during the loading phase: Lateral Quadriceps (LQ) and Lateral Hamstrings (LH), LQ:LH; LQ and Lateral Gastrocnemius (LG), LQ:LG; Medial Quadriceps (MQ) and Medial Hamstrings (MH), MQ:MH; MQ and Medial Gastrocnemius (MG), MQ:MG; and Tibialis Anterior (TA) and LG, TA:LG. Four stepwise multiple linear regression analyses were performed using CPF as dependent variable. One regression was performed for each condition (gait and step-down) and each leg (MA and LA). Independent variables were joint excursions and mean CC of muscle pairs respective to each condition and leg. Gender, age, height and mass were controlled for their potential confounding effects. Independent variables were entered in a stepwise manner. Probability of F change was set at 0.1 to enter and 0.15 for removal. Results: In all four regression analyses, after controlling for demographic variables, decreased joint excursion and increased CC explained additional variability in CPF. During the gait conditions, LQ:LH explained additional variability in CPF on both legs, whereas ankle excursion explained additional variability only on the LA leg. During LA step down, TA:LG, LQ:LH, and ankle excursion explained additional variability in CPF. On the MA leg step down, MQ:MH and hip excursion explained additional variability in CPF (Table 1).