Shawn M. Robbins

The effect of gait speed on the knee adduction moment depends on waveform summary measures.

The external knee adduction moment (KAM) is a useful proxy for medial knee loading. Though many studies examining the KAM report the peak value, recent studies have evaluated other measures from this waveform, including the stance impulse. It is important to understand the impact of varying gait speed on discrete values of the KAM waveform when evaluating differences between samples. The purpose of this study was to compare measures of the KAM waveform, including peak and impulse, during level walking at different speeds. Thirty-two healthy participants (mean age=32+/-8 years, 18 women) were recruited. The KAM peak and impulse were calculated over three ambulation speeds: self-selected, slow (15% slower than self-selected) and fast (15% faster than self-selected). To identify differences between these conditions, a one-way repeated measures analysis of variance was utilized. The peak KAM was greater in the fast compared to the slow condition (p<0.05). The KAM impulse was greater in the slow compared to both self-selected and fast conditions (p<0.05). The KAM impulse appeared more sensitive to changes in gait speed because the impulse reflects the duration of loading. These findings highlight that slowed gait speed increased loading exposure on the medial knee tissues, though the maximum magnitude of the exposure was reduced. This trade-off between the increase in duration and decrease in amplitude at slower gait speeds should be examined, particularly where loading exposure may lead to pathology, such as knee osteoarthritis.

Efficacy of Exercise Intervention as Determined by the McKenzie System of Mechanical Diagnosis and Therapy for Knee Osteoarthritis: A Randomized Controlled Trial

STUDY DESIGN Randomized controlled trial. Objectives To examine the efficacy of exercise intervention in patients with knee osteoarthritis (OA), as directed by Mechanical Diagnosis and Therapy (MDT) assessment, and, secondarily, to explore outcomes between MDT assessment-defined subgroups within the exercise group. BACKGROUND Due to the high physical and economic burden of knee OA, the effectiveness of conservative interventions and determining those patients who will respond to them should be investigated. METHODS Patients with knee OA (n = 180) were randomized to an exercise intervention group or a control group. The intervention group, in which patients classified as having knee derangements (MDT derangement) received MDT directional exercises and patients classified as nonresponders (MDT nonresponders) received evidence-based exercises, was compared to a control group that received no exercise intervention. Pain and function were assessed at baseline, 2 weeks, and 3 months, using the P4 pain scale and Knee injury and Osteoarthritis Outcome Score (KOOS) pain and function subscales. Two-way analysis of covariance was used to examine treatment and time effects. Multiple comparisons were examined, and mean differences with 95% confidence intervals (CIs) were reported. RESULTS The exercise intervention group had significantly improved P4 scores (mean difference, -6; 95% CI: -8, -3), KOOS pain scores (mean difference, 9; 95% CI: 5, 13), and KOOS function scores (mean difference, 11; 95% CI: 7, 15) compared to those of the control group at 2 weeks. At 3 months, the exercise intervention group had significantly improved KOOS pain scores (mean difference, 7; 95% CI: 3, 11) and KOOS function scores (mean difference, 5; 95% CI: 1, 9) compared to controls. CONCLUSION Patients with knee OA who were prescribed exercises based on an MDT assessment had superior outcomes compared to those of wait-list controls. The MDT subgroup of knee derangement may warrant further investigation in patients with knee OA. Protocol registered at ClinicalTrials.gov (NCT01641874). LEVEL OF EVIDENCE Therapy, level 1b-.

Association of pain with frequency and magnitude of knee loading in knee osteoarthritis

Although the relationship between pain and the magnitude of medial knee loading has been previously studied, the contribution of frequency of loading has not. The objective of this study was to determine whether the addition of loading frequency (steps/day) to loading magnitude (knee adduction moment [KAM] impulse) helps explain variance in knee pain in people with knee osteoarthritis (OA).

Developing an estimate of daily cumulative loading for the knee: Examining test–retest reliability

Although the knee adduction moment during gait is a valid and reliable proxy for the dynamic load on the medial compartment of the knee, it represents exposure to loading during one stride only. In contrast, a measure that incorporates both the nature and frequency of loading throughout daily activities might provide additional insight into the effects of cumulative knee loading. The purpose of this study was to introduce a new representation of daily cumulative knee loading and examine its test-retest reliability. Thirty healthy adults participated. Cumulative knee loading was calculated on two testing periods from the mean external knee adduction moment stance phase impulse, measured with a three-dimensional motion capture system over five walking trials, and mean steps/day, measured with a unidimensional accelerometer over one week. Analysis for test-retest reliability included Bland-Altman graphs, intraclass correlation coefficients (ICC 2,1) and standard errors of measurements (SEM). The ICC values for cumulative knee loading, adduction impulse and steps/day ranged from 0.84 to 0.89. Bland-Altman plots suggested daily cumulative knee loading and steps/day measures were less reliable at higher values. The SEM values were 9.67 kNm s, 1.45 Nm s and 1043 steps/day for cumulative knee loading, adduction impulse and steps/day, respectively. Daily cumulative knee loading is reliable and provides a stable measure of the total exposure to knee loading. These findings support further study of cumulative knee loading to determine its potential clinical importance.

Cumulative knee adductor load distinguishes between healthy and osteoarthritic knees–A proof of principle study

Cumulative knee adductor load reflects repetitive exposures to medial knee loading that are encountered during daily activity. The purpose of this proof of principle study was to investigate whether cumulative knee adductor load distinguished between adults with and without knee osteoarthritis (OA). Thirty-one adults with radiographic knee OA (53.2±6.1 years old) and 30 healthy adults (33.5±8.0 years old) participated. A non-normalized knee adduction moment waveform was calculated from gait data collected using a motion analysis system with synchronized force plate. The peak and impulse from knee adduction moment was calculated. Cumulative knee adductor load was the product of the knee adduction moment impulse during stance and the mean number of steps taken per day, measured with a uni-dimensional accelerometer. One thousand bootstrap t-tests determined whether cumulative knee adductor load was at least as good as the peak knee adduction moment in discriminating between the healthy and OA groups. Cumulative knee adductor load was nearly two times larger in the knee OA compared to the healthy group (p=0.001). Cumulative knee adductor load was better than the peak knee adduction moment at discriminating between groups (p=0.04). This work provides evidence of validity for cumulative knee adductor load. In the calculation of cumulative loads, non-normalization of the adduction moment impulse to magnitude or time emphasized the importance of the total loads borne through the medial knee compartment during each step.

Reliability of surface electromyographic recordings during walking in individuals with knee osteoarthritis

To determine test-retest reliability of a surface electromyographic protocol designed to measure knee joint muscle activation during walking in individuals with knee osteoarthritis (OA). Twenty-one individuals with moderate medial compartment knee OA completed two gait data collections separated by approximately 1month. Using a standardized protocol, surface electromyograms from rectus femoris plus lateral and medial sites for the gastrocnemii, vastii and hamstring muscles were recorded during walking. After full-wave rectification and low pass filtering, time and amplitude normalized (percent of maximum) waveforms were calculated. Principal component analysis (PP-scores) and co-contraction indices (CCI) were calculated from the waveforms. Intraclass correlation coefficients (ICC2,k) were calculated for PP-scores and CCIs. No differences in walking speed, knee muscle strength and symptoms were found between visits (p>0.05). The majority of PP-scores (17 of 21) and two of four CCIs demonstrated ICC2,k values greater than 0.81. Remaining PP-scores and CCIs had ICC2,k values between 0.61 and 0.80. The results support that reliable EMG characteristics can be captured from a moderate knee OA patient population using a standardized protocol.

Reliability of principal components and discrete parameters of knee angle and moment gait waveforms in individuals with moderate knee osteoarthritis

Gait measures are used to evaluate change in patients with knee osteoarthritis (OA), but reliability has not been fully established in this population. This study examined test-retest reliability of knee angle and moment gait waveform characteristics captured using discrete parameters and principal component analysis (PCA) in individuals with moderate knee OA. Participants (n=20) underwent three-dimensional gait analysis on two occasions. Motion and force data were captured using two camera banks, infrared light emitting diodes and force plate during self-selected walking. Knee angle and moment waveforms were calculated and analyzed using discrete parameters and by identifying waveform characteristics using PCA. Intraclass correlation coefficients (ICC2,k) examined test-retest reliability of discrete parameters and PCA derived scores (PC-scores). ICC2,k values ranged from 0.57 to 0.93 for discrete parameters, 0.52-0.86 for knee angle PC-scores and 0.30-0.94 for the knee moment PC-scores. However, 10 of 13 discrete parameters, six of nine knee angle PC-scores and seven of nine knee moment PC-scores had ICC2,k values greater than or equal to 0.70. Discrete parameters and PC-scores from flexion angles and adduction moments had the highest ICC2,k values while adduction angles, rotation angles, and rotation moments had the lowest. Most knee angle and moment waveform characteristics demonstrated ICC2,k values that could be interpreted as acceptable. Caution should be used when examining adduction and rotation angle magnitudes and early/mid-stance rotation moment magnitudes due to lower ICC2,k values.

Osteoarthritis Year in Review 2014: rehabilitation and outcomes

OBJECTIVE To highlight research studies examining rehabilitation for hip and knee osteoarthritis (OA), as well as the outcome measures used to assess treatment efficacy, published in 2013. DESIGN A systematic search was performed in Medline, CIHAHL and Embase databases from January to December 2013. The search was limited to 2013, human studies, and English. Rehabilitation intervention studies included were prospective controlled designs. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used to evaluate the quality of evidence. First, individual articles were rated for quality. Second, articles were grouped based on outcome: OA disease markers, pain, physical function (self-reported, performance), and health. RESULTS Of 503 titles reviewed, 36 studies were included. The outcome measures related to OA disease markers were organized into subthemes of anthropometrics, biomechanics and physiology. The quality of evidence was of moderate, high, and low quality for anthropometric, biomechanical and physiological measures respectively. These studies supported the use of diet for weight loss combined with exercise. Bodies of evidence that showed the efficacy of exercise and passive strategies (thermal/electrical modalities, traction, manual therapy) for reducing pain were of low and moderate quality respectively. The evidence supporting diet and exercise, physiotherapy, and passive strategies to improve physical function was of moderate quality. Evidence supporting exercise to improve psychological factors was of moderate quality. CONCLUSIONS Exercise combined with diet for weight loss should be the mainstays of rehabilitation for people with knee and hip OA to provide benefit to OA disease markers, pain, physical function, and health.

Comparative diagnostic accuracy of knee adduction moments in knee osteoarthritis: A case for not normalizing to body size

Previous authors have questioned the practice of normalizing the external knee adduction moment during gait to body size when investigating dynamic joint loading in knee osteoarthritis (OA). The purpose of this study was to compare the abilities of non-normalized and normalized external knee adduction moments during gait in discriminating between patients with least and greatest severity of radiographic medial compartment knee OA. Subjects with mild (n=118) and severe (n=115) medial compartment knee OA underwent three-dimensional gait analysis. The peak external knee adduction moment was calculated and kept in its original units (Nm), normalized to body mass (Nm/kg) and normalized to body weight and height (%BW × Ht). Receiver Operating Characteristic (ROC) curve analysis indicated that non-normalized values better discriminated between patients with mild and severe knee OA. The area under the ROC curve for non-normalized peak knee adduction moments (0.63) was significantly (p<0.05) greater than when normalized to body mass (0.58), or to body weight times height (0.57). Post-hoc analysis of covariance indicated the mean difference in peak knee adduction moment between OA severity groups (7.23 Nm, p=0.003) was reduced by approximately 50% (3.60 Nm, p=0.09) when adjusted for mass. These findings are consistent with the suggestion that non-normalized values are more sensitive to radiographic disease progression. We suggest including knee adduction moment values that are not normalized to body size when investigating knee OA.

Longitudinal changes in the lower extremity functional scale after anterior cruciate ligament reconstructive surgery.

Objective:To describe the pattern of change in lower extremity physical function status as measured by the Lower Extremity Functional Scale (LEFS) during the first 16 weeks after anterior cruciate ligament (ACL) reconstructive surgery and illustrate how this information can be applied in clinical practice to assist with goal setting and the evaluation of patient outcomes. The secondary objective is to estimate the test-retest reliability of the LEFS in this population. Design:Prospective cohort, observational. Setting:Physiotherapy private practice. Patients:Forty-seven participants underwent ACL reconstructive surgery and were initially recruited. Two participants were excluded from the analysis, resulting in 45 participants (28 men, mean age 29.4 years; 17 women, mean age 29.0 years). Interventions:Participants underwent a rehabilitation protocol. Main Outcome Measures:Participants completed the LEFS at each visit from their initial physiotherapy session to 16 weeks postsurgery. A nonlinear model of change was developed, which related LEFS scores to weeks postsurgery. Test-retest reliability was examined between the seventh and ninth weeks using intraclass correlation coefficients (ICC2,1) and standard error of measurement (SEM). Results:The nonlinear model demonstrated rapid improvements in LEFS scores within the first 7 to 8 weeks with a gradual tapering of this improvement. At 16 weeks, the predicted LEFS score was 63 out of a maximum score of 80. The LEFS demonstrated excellent test-retest reliability in this population (ICC2,1 = 0.90, SEM = 3.7). Conclusions:This study provides a description of postsurgical change in functional status for patients after ACL reconstructive surgery that can assist clinicians in developing clinical goals. Clinical Relevance:A rapid improvement in lower extremity physical function is demonstrated in the first 7 to 8 weeks after ACL reconstructive surgery with a tapering of this improvement after 8 weeks.