Clinical Biomechanics

Editorial Board

2012-06-01

Investigating the change in three dimensional deformity for idiopathic scoliosis using axially loaded MRI

J.P. Little, M.T. Izatt, R.D. Labrom, G.N. Askin, C.J. Adam — 2012-01-06

Abstract: Background: Adolescent idiopathic scoliosis is a complex three-dimensional deformity, involving a lateral deformity in the coronal plane and axial rotation of the vertebrae in the transverse plane. Gravitational loading plays an important biomechanical role in governing the coronal deformity, however, less is known about how they influence the axial deformity. This study investigates the change in three-dimensional deformity of a series of scoliosis patients due to compressive axial loading.Methods: Magnetic resonance imaging scans were obtained and coronal deformity (measured using the coronal Cobb angle) and axial rotations measured for a group of 18 scoliosis patients (Mean major Cobb angle was 43.4o). Each patient was scanned in an unloaded and loaded condition while compressive loads equivalent to 50% body mass were applied using a custom developed compressive device.Findings: The mean increase in major Cobb angle due to compressive loading was 7.4o (SD 3.5o). The most axially rotated vertebra was observed at the apex of the structural curve and the largest average intravertebral rotations were observed toward the limits of the coronal deformity. A level-wise comparison showed no significant difference between the average loaded and unloaded vertebral axial rotations (intra-observer error=2.56o) or intravertebral rotations at each spinal level.Interpretation: This study suggests that the biomechanical effects of axial loading primarily influence the coronal deformity, with no significant change in vertebral axial rotation or intravertebral rotation observed between the unloaded and loaded condition. However, the magnitude of changes in vertebral rotation with compressive loading may have been too small to detect given the resolution of the current technique.

Describing the active region boundary of EMG-assisted biomechanical models of the low back

Xiaopeng Ning, Sangeun Jin, Gary A. Mirka — 2011-12-15

Abstract: Background: Electromyography-assisted (EMG-assisted) biomechanical models are used to characterize the muscle and joint reaction forces in the lumbar region. However, during a full-range trunk flexion, there is a transition of extension moment from the trunk extensor muscles to the passive tissues of the low back, indicating that the empirical EMG data used to drive these EMG-assisted models becomes less correlated with the extensor moment. The objectives of this study were to establish the trunk flexion angles at which the passive tissues generate substantial trunk extension moment and to document how these angles change with asymmetry.Methods: Participants performed controlled trunk flexion–extension motions in three asymmetric postures. The trunk kinematics data and the electromyographic activity from L3- and L4-level paraspinals and rectus abdominis were captured. The time-dependent net internal active moment (from an EMG-assisted model) and the net external moment were calculated. The trunk and lumbar angles at which the net internal active moment was less than 70% of the external moment were found.Findings: The trunk flexion angle at which the net internal moment reaches the stated criteria varied as a function of asymmetry of trunk flexion motion with the sagittally symmetric case providing the deepest flexion angle of 38° (asymmetry 15°: 33°; asymmetry 30°: 26°).Interpretation: These results indicate that EMG-assisted biomechanical models need to consider the role of passive tissues at trunk flexion angles significantly less than previously thought and these flexion angles vary as a function of the asymmetry and direction of motion.

Comparison of shoulder load during power-assisted and purely hand-rim wheelchair propulsion

2011-12-30

Abstract: Background: Repetitive forces and moments are among the work requirements of hand-rim wheelchair propulsion that are related to shoulder injuries. No previous research has been published about the influence of power-assisted wheelchair propulsion on these work requirements. The purpose of our study was therefore to determine the influence of power-assisted propulsion on shoulder biomechanics and muscle activation patterns. We also explored the theoretical framework for the effectiveness of power-assisted propulsion in preventing shoulder injuries by decreasing the work requirements of hand-rim wheelchair propulsion.Methods: Nine non-wheelchair users propelled a hand-rim wheelchair on a treadmill at 0.9m/s. Shoulder biomechanics, and muscle activation patterns, were compared between propulsion with and without power-assist.Findings: Propulsion frequency did not differ significantly between the two conditions (Wilcoxon Signed Rank test/significance level/effect size:4/.314/−.34). During power-assisted propulsion we found significantly decreased maximum shoulder flexion and internal rotation angles (1/.015/−.81 and0/.008/−.89) and decreased peak force on the rim (0/.008/−.89). This resulted in decreased shoulder flexion, adduction and internal rotation moments (2/.021/−.77; 0/.008/−.89 and1/.011/−.85) and decreased forces at the shoulder in the posterior, superior and lateral directions (2/.021/−.77; 2/.008/−.89 and2/.024/−.75). Muscle activation in the pectoralis major, posterior deltoid and triceps brachii was also decreased (2/.038/−.69; 1/.015/−.81 and 1/.021/−.77).Interpretation: Power-assist influenced the work requirements of hand-rim wheelchair propulsion by healthy subjects. It was primarily the kinetics at rim and shoulder which were influenced by power-assisted propulsion. Additional research with actual hand-rim wheelchair users is required before extrapolation to routine clinical practice.

The effect of clavicle malunion on shoulder biomechanics; A computational study

Bipin Patel, Peter A. Gustafson, James Jastifer — 2012-01-09

Abstract: Background: Clavicle malunion affects the biomechanics of the shoulder joint. The purpose of this study is to establish the abduction, flexion, and internal (medial) rotation biomechanics of the shoulder after clavicle malunion.Methods: A computational study was performed utilizing a three-dimensional, validated computational model of the upper extremity. Sequential shortening of the clavicle up to 20% was simulated. Muscle forces, moment arms, and moments were calculated for the surrounding musculature through a range of flexion, abduction, and internal rotation during the simulated shortening.Findings: Shortening of the clavicle decreases the shoulder elevation moments of the upper extremity muscles during abduction. Internal rotation moments are also decreased with shortening. Flexion moments were affected less through physiologic range of motion. The observed effects are due to a combination of changes in moment arms of the individual muscles as well as a decrease in the force generating capacity of the muscles. Additionally, shortening of the clavicle increases coronal angulation of the clavicle at the sternoclavicular joint.Interpretation: Shortening causes a decrease in the moment generating capacity as well as the total force generating capacity of the shoulder girdle muscles. The clinical significance of these computational results, which are consistent with recent clinical studies, is validation of the proposed functional deficit caused by clavicle malunion.

Importance of polyethylene thickness in total shoulder arthroplasty: A finite element analysis

Alexandre Terrier, Vittoria Brighenti, Dominique P. Pioletti, Alain Farron — 2012-01-06

Abstract: Background: Articular surfaces reconstruction is essential in total shoulder arthroplasty. Because of the limited glenoid bone support, thin glenoid component could improve anatomical reconstruction, but adverse mechanical effects might appear.Methods: With a numerical musculoskeletal shoulder model, we analysed and compared three values of thickness of a typical all-polyethylene glenoid component: 2, 4 (reference) and 6mm. A loaded movement of abduction in the scapular plane was simulated. We evaluated the humeral head translation, the muscle moment arms, the joint force, the articular contact pattern, and the polyethylene and cement stress.FindingsDecreasing polyethylene thickness from 6 to 2mm slightly increased humeral head translation and muscle moment arms. This induced a small decreased of the joint reaction force, but important increase of stress within the polyethylene and the cement mantel.InterpretationThe reference thickness of 4mm seems a good compromise to avoid stress concentration and joint stuffing.

Range of motion of the metacarpophalangeal joint in rheumatoid patients, with and without a flexible joint replacement prosthesis, compared with normal subjects

2012-01-20

Abstract: Background: The metacarpophalangeal is commonly affected by rheumatoid arthritis. This may lead to joint replacement with a flexible prosthesis. The aims of this study were to determine the effects of rheumatoid arthritis on joint motion and to determine whether joint replacement needs to restore the full range of motion.Methods: Three-dimensional motion analysis was used to measure the range of motion of the metacarpophalangeal joint in rheumatoid patients with and without a flexible silicone arthroplasty, when performing pinch and key grips, when making a fist and when spreading the fingers. The results were compared with those from younger and older normal subjects.Findings: There appeared to be a trend for a decrease in range of motion from younger normal to older normal to rheumatoid (no prosthesis) to rheumatoid (with prosthesis) subject groups. However, statistically different (p<0.05) results were only observed for some movements (mostly involved in making a fist), in some fingers and between some subject groups. The only exception to this apparent trend was in flexion/extension when spreading the fingers into abduction.Interpretation: Making a fist is the most sensitive simple measure of range of motion in the metacarpophalangeal joint. Successful replacement of the metacarpophalangeal joint in patients with rheumatoid arthritis need not restore the normal range of motion.

Effects of the index finger position and force production on the flexor digitorum superficialis moment arms at the metacarpophalangeal joints — a magnetic resonance imaging study

Joel R. Martin, Mark L. Latash, Vladimir M. Zatsiorsky — 2011-12-22

Abstract: Background: The purpose of this study was to use magnetic resonance imaging to measure the moment arm of the flexor digitorum superficialis tendon about the metacarpophalangeal joint of the index, middle, ring, and little fingers when the position and force production level of the index finger was altered. A secondary goal was to create regression models using anthropometric data to predict moment arms of the flexor digitorum superficialis about the metacarpophalangeal joint of each finger.Methods: The hands of subjects were scanned using a 3.0T magnetic resonance imaging scanner. The metacarpophalangeal joint of the index finger was placed in: flexion, neutral, and extension. For each joint configuration subjects produced no active force (passive condition) and exerted a flexion force to resist a load at the fingertip (active condition).Results: The following was found: (1) The moment arm of the flexor digitorum superficialis at the metacarpophalangeal joint of the index finger (a) increased with the joint flexion and stayed unchanged with finger extension; and (b) decreased with the increase of force at the neutral and extended finger postures and did not change at the flexed posture. (2) The moment arms of the flexor digitorum superficialis tendon of the middle, ring, and little fingers (a) did not change when the index metacarpophalangeal joint position changed (P>0.20); and (b) The moment arms of the middle and little fingers increased when the index finger actively produced force at the flexed metacarpophalangeal joint posture. (4) The moment arms showed a high correlation with anthropometric measurements.Interpretation: Moment arms of the flexor digitorum superficialis change due to both changes in joint angle and muscle activation; they scale with various anthropometric measures.

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

Kenton R. Kaufman, Serena Frittoli, Carlo A. Frigo — 2012-01-05

Abstract: Background: Amputees walk with an asymmetrical gait, which may lead to future musculoskeletal degenerative changes. The purpose of this study was to compare the gait asymmetry of active transfemoral amputees while using a passive mechanical knee joint or a microprocessor-controlled knee joint.Methods: Objective 3D gait measurements were obtained in 15 subjects (12 men and 3 women; age 42, range 26–57). Research participants were longtime users of a mechanical prosthesis (mean 20years, range 3–36years). Joint symmetry was calculated using a novel method that includes the entire waveform throughout the gait cycle.Findings: There was no significant difference in hip, knee and ankle kinematics symmetry when using the different knee prostheses. In contrast, the results demonstrated a significant improvement in lower extremity joint kinetics symmetry when using the microprocessor-controlled knee.Interpretation: Use of the microprocessor-controlled knee joint resulted in improved gait symmetry. These improvements may lead to a reduction in the degenerative musculoskeletal changes often experienced by amputees.

Whole body kinematics and knee moments that occur during an overhead catch and landing task in sport

2012-01-13

Abstract: Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task.Methods: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments.FindingsLanding after an overhead catch when the ball moved towards a player's support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.InterpretationLearning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete's risk of non-contact anterior cruciate ligament injury.

Tibial rotation in anterior cruciate ligament reconstructed knees during single limb hop and drop landings

Kate E. Webster, Julian A. Feller — 2012-01-13

Abstract: Background: Alterations in knee joint kinematics have been suggested as a potential mechanism that influences the development of osteoarthritis of the knee after anterior cruciate ligament reconstruction. Whilst previous work has shown changes in internal–external tibial rotation during level walking, many patients aim to return to high impact activities following surgery. This study examined tibial rotation during single limb hop and drop landings in anterior cruciate ligament reconstructed knees compared to a control group, and also evaluated the influence of graft type (hamstring or patellar tendon).Methods: In 48 participants (17 patellar tendon graft, 18 hamstring graft and 13 controls) internal–external rotation was measured during single limb hop and drop landings in a gait laboratory at mean of 10months after surgery.Findings: There was no difference between the two graft types and both patient groups had less internal rotation when compared to the control group. For 60% of patients, internal rotation values were at least 5° less than the control group mean.Interpretation: Anterior cruciate ligament reconstructed knees with both hamstring tendon and patellar tendon grafts show altered rotational kinematic patterns during high impact dynamic load activities.

Tibial rotation during pivoting in anterior cruciate ligament reconstructed knees using a single bundle technique

Kate E. Webster, Simon E. Palazzolo, Jodie A. McClelland, Julian A. Feller — 2011-12-12

Abstract: Background: Anterior cruciate ligament reconstruction does not necessarily restore normal knee movement. Increased tibial rotation has previously been noted during pivoting activities and may be due to the orientation of the anterior cruciate ligament graft associated with traditional single bundle reconstruction techniques. Recent research has shown that it is possible to limit rotation during level walking using a single bundle anterior cruciate ligament reconstruction. This study evaluated rotational knee kinematics during a pivot task in a group of patients who had undergone anterior cruciate ligament reconstruction using a single bundle technique and compared the findings to a normal control group.Methods: In 27 anterior cruciate ligament reconstruction and 25 control participants, internal–external rotation was measured during a descend stairs and pivot task in a gait laboratory.Findings: Results showed that the anterior cruciate ligament reconstruction patients had less internal tibial rotation (for both range of rotation and maximum rotation) than the control participants (effect size=0.7).Interpretation: These results suggest that it is possible to limit rotation after anterior cruciate ligament reconstruction using a single bundle technique, even during a pivoting movement that places a high rotational load at the knee joint. The positioning of the femoral tunnel in a more anatomical position may be responsible for the reduced tibial rotation.

Determinants of co-contraction during walking before and after arthroplasty for knee osteoarthritis

2011-12-08

Abstract: Background: Knee osteoarthritis patients co-contract in knee-related muscle pairs during walking. The determinants of this co-contraction remain insufficiently clear.Methods: A heterogeneous group of 14 patients was measured before and one year after knee arthroplasty, and compared to 12 healthy peers and 15 young subjects, measured once. Participants walked on a treadmill at several imposed speeds. Bilateral activity of six muscles was registered electromyographically, and co-contraction time was calculated as percentage of stride cycle time. Local dynamic stability and variability of sagittal plane knee movements were determined. The surgeon's assessment of alignment was used. Pre-operatively, multivariate regressions on co-contraction time were used to identify determinants of co-contraction. Post-operatively it was assessed if predictor variables had changed in the same direction as co-contraction time.Findings: Patients co-contracted longer than controls, but post-operatively, differences with the healthy peers were no longer significant. Varus alignment predicted co-contraction time. No patient had post-operative varus alignment. The patients' unaffected legs were more unstable, and instability predicted co-contraction time in both legs. Post-operatively, stability normalised. Longer unaffected side co-contraction time was associated with reduced affected side kinematic variability. Post-operatively, kinematic variability had further decreased.Interpretations: Varus alignment and instability are determinants of co-contraction. The benefits of co-contraction in varus alignment require further study. Co-contraction probably increases local dynamic stability, which does not necessarily decrease the risk of falling. Unaffected side co-contraction contributed to decreasing affected side variability, but other mechanisms than co-contraction may also have played a role in decreasing variability.

The contribution of quasi-joint stiffness of the ankle joint to gait in patients with hemiparesis

2012-01-09

Abstract: Background: The role of ankle joint stiffness during gait in patients with hemiparesis has not been clarified. The purpose of this study was to determine the contribution of quasi-joint stiffness of the ankle joint to spatiotemporal and kinetic parameters regarding gait in patients with hemiparesis due to brain tumor or stroke and healthy individuals.Methods: Spatiotemporal and kinetic parameters regarding gait in twelve patients with hemiparesis due to brain tumor or stroke and nine healthy individuals were measured with a 3-dimensional motion analysis system. Quasi-joint stiffness was calculated from the slope of the linear regression of the moment–angle curve of the ankle joint during the second rocker.Findings: There was no significant difference in quasi-joint stiffness among both sides of patients and the right side of controls. Quasi-joint stiffness on the paretic side of patients with hemiparesis positively correlated with maximal ankle power (r=0.73, P<0.01) and gait speed (r=0.66, P<0.05). In contrast, quasi-joint stiffness in controls negatively correlated with maximal ankle power (r=−0.73, P<0.05) and gait speed (r=−0.76, P<0.05).Interpretation: Our findings suggested that ankle power during gait might be generated by increasing quasi-joint stiffness in patients with hemiparesis. In contrast, healthy individuals might decrease quasi-joint stiffness to avoid deceleration of forward tilt of the tibia. Our findings might be useful for selecting treatment for increased ankle stiffness due to contracture and spasticity in patients with hemiparesis.

Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs

Ryan Chang, Jane A. Kent-Braun, Joseph Hamill — 2011-12-14

Abstract: Background: Due to complexity of the plantar intrinsic foot muscles, little is known about their muscle architecture in vivo. Chronic plantar fasciitis may be accompanied by muscle atrophy of plantar intrinsic foot muscles and tibialis posterior compromising the dynamic support of the foot prolonging the injury. Magnetic resonance images of the foot may be digitized to quantify muscle architecture. The first purpose of this study was to estimate in vivo the volume and distribution of healthy plantar intrinsic foot muscles. The second purpose was to determine whether chronic plantar fasciitis is accompanied by atrophy of plantar intrinsic foot muscles and tibialis posterior.Methods: Magnetic resonance images were taken bilaterally in eight subjects with unilateral plantar fasciitis. Muscle perimeters were digitally outlined and muscle signal intensity thresholds were determined for each image for volume computation.Findings: The mean volume of contractile tissue in healthy plantar intrinsic foot muscles was 113.3cm3. Forefoot volumes of plantar fasciitis plantar intrinsic foot muscles were 5.2% smaller than healthy feet (P=0.03, ES=0.26), but rearfoot (P=0.26, ES=0.08) and total foot volumes (P=0.07) were similar. No differences were observed in tibialis posterior size.Interpretations: While the total volume of plantar intrinsic foot muscles was similar in healthy and plantar fasciitis feet, atrophy of the forefoot plantar intrinsic foot muscles may contribute to plantar fasciitis by destabilizing the medial longitudinal arch. These results suggest that magnetic resonance imaging measures may be useful in understanding the etiology and rehabilitation of chronic plantar fasciitis.

Comparison of elastic versus rigid suture material for peripheral sutures in tendon repair

Kenji Nozaki, Ryuji Mori, Koji Ryoke, Yuji Uchio — 2011-12-15

Abstract: Background: For secure tendon repair, while core suture materials have been previously investigated, the optimum material for peripheral sutures remains unclear.Methods: Transected bovine gastrocnemius tendons were repaired by 2-strand side-locking loop technique using no.2 braided polyblend polyethylene thread for the core suture. Then, 8-strand peripheral cross-stitches were added using either 2–0 rigid sutures (braided polyblend polyethylene) or USP 2-0-sized elastic sutures (nylon). The holding area of each peripheral suture was set at either 3×1mm (shallow holding) or 6×2mm (deep holding). Therefore, 4 groups were compared (the shallow-rigid, deep-rigid, shallow-elastic, and deep-elastic groups). The gap formation, ultimate tensile strength, and suture migration state were measured after 500 cyclic loadings (from 10 to 200N).Methods: The shallow-rigid group had inferior outcomes compared to the other groups. Although the deep-rigid group had the smallest gap and highest ultimate strength, all peripheral sutures had failure prior to core suture rupture. The two elastic groups showed no significant differences, irrespective of the size of the holding area. Suture migration did not occur in the two elastic groups until the ultimate strength was reached and the core suture ruptured.Interpretation: Depending on the suturing method, rigid suture material may not be appropriate for peripheral sutures, when accompanying rigid core suture material. If peripheral sutures can be made with accurate deep holding, rigid suture material will provide favorable outcome. However, in other cases, elastic suture material is considered best for supporting a rigid core suture, as elasticity is another important factor for peripheral sutures.

Segment choice and cup stability influence wear measurements using radiostereometric analysis: A radiostereometric study comparing wear measured by markers in the polyethylene with markers in the periacetabular bone

Einar Lindalen, Lars Nordsletten, Stephan M. Röhrl — 2011-12-26

Abstract: Background: Radiostereometry is a well documented method to measure the polyethylene wear after total hip replacements. Wear is measured according to the point motion of the head center in relation to the polyethylene as the reference segment. Increasing head sizes and new cup materials may diminish visibility of markers deteriorating the segment and leading to study drop outs. Alternatively markers in the periacetabular bone may be easier to detect rendering this segment more stable. Our aim was to compare wear measurements against the cup, the acetabuluar bone and a calculated wear estimation including cup migration.Methods: A prospective randomized controlled trial comparing reverse hybrid with cemented total hip replacement was conducted. 31 patients had tantalum markers in the polyethylene and in the periacetabular bone making it possible to measure wear using both as reference segments. We used a uniplanar radiostereometric technique.Findings: Wear in the y-axis was overestimated by 53% when markers in the periacetabular bone were used (P<0.001). Proximal wear was 0.34mm (95% CI of mean: 0.29–0.38) when using the polyethylene as the reference and 0.52mm (95% CI of mean: 0.38–0.65) using the acetabular bone. Migration of the cup seemed to influence the wear calculations, overestimating wear when markers in the periacetabular bone were used as the reference segment.Interpretation: Wear measured with periacatebular bone markers is influenced by cup migration, overestimating wear measurements. We therefore recommend not using the acetabular bone as the reference segment.

Effective lubrication of articular cartilage by an amphiphilic hyaluronic acid derivative

Antonella Schiavinato, Robert A. Whiteside — 2012-01-04

Abstract: Background: Intra-articular injection of hyaluronic acid based therapies is gaining popularity as a treatment option for non-operative management of patients with symptomatic osteoarthritis. Although there is an abundance of evidence for both biological and mechanical mechanisms of joint protection by hyaluronic acid, one clear intention of viscosupplementation is to reduce friction and wear by providing an extrinsic lubricant. We tested the in vitro friction response of a novel hyaluronic acid derivative that presents amphiphilic features to promote adhesion to the cartilage surface and thereby improve cartilage lubrication.Methods: Migrating Contact Area and Static Contact Area friction tests were conducted on bovine articular cartilage to assess the efficacy of two lubricants, a chemically modified amphiphilic hyaluronic acid and synovial fluid from a healthy joint, as well as a phosphate buffered saline negative control.Findings: No differences in lubrication (P=0.34) were evident between the three test articles during the Migrating Contact Area test, which represents articulation of healthy articular cartilage.The modified hyaluronic acid presented an equilibrium friction coefficient 2.8 times less than that of the synovial fluid (P≤0.0005) and five times less than that of the PBS control (P≤0.0001) during the Static Contact Area test, representing a mixed lubrication condition.Interpretation: The present study demonstrated that a chemically modified amphiphilic hyaluronic acid can provide equivalent lubrication to synovial fluid during articulation of loaded healthy articular cartilage and can provide superior lubrication as indicated by a lower coefficient of friction than synovial fluid under loading conditions potentially associated with cartilage wear.

Comparison of peak knee adduction moment and knee adduction moment impulse in distinguishing between severities of knee osteoarthritis

2012-01-13

Abstract: Background: The peak knee adduction moment is a valid proxy for medial knee joint loading. However as it only measures load at one instance of stance, knee adduction moment impulse, a measure that takes into account both the magnitude and duration of the stance phase, may provide more comprehensive information. This study directly compared the abilities of peak knee adduction moment and knee adduction moment impulse to distinguish between knee osteoarthritis severities.Methods: 169 participants with medial knee osteoarthritis completed radiographic and magnetic resonance imaging, the Western Ontario and McMaster Universities Arthritis Index to assess pain and a three-dimensional gait analysis. Participants were classified using four dichotomous classifications: Kellgren–Lawrence grading, alignment, medial tibiofemoral bone marrow lesions, and pain.Findings: When using Kellgren–Lawrence grade and alignment classifications, the area under the receiver operator curves were significantly greater for knee adduction moment impulse than for peak knee adduction moment. Based on analysis of covariance, knee adduction moment impulse was significantly different between Kellgren–Lawrence grade and alignment groups while peak knee adduction moment was not significantly different. Both peak knee adduction moment and knee adduction moment impulse distinguished between bone marrow lesion severities while neither measure was significantly different between pain severity groups.Interpretations: Findings suggest knee adduction moment impulse is more sensitive at distinguishing between disease severities and may provide more comprehensive information on medial knee joint loading. Future studies investigating biomechanics of knee osteoarthritis should include knee adduction moment impulse in conjunction with peak knee adduction moment.

The Society for Back Pain Research Annual General Meeting 2012

2012-06-01