Kirsten C. Moisio

Normalization of joint moments during gait: a comparison of two techniques

Joint moments are commonly used to characterize gait. Factors like height and weight influence these moments. This study determined which of two commonly used normalization methods, body mass or body weight times height, most reduced the effects of height and weight on peak hip, knee, and ankle external moments during walking. The effectiveness of each normalization method in reducing gender differences was then tested. Gait data from 158 normal subjects were analyzed using unnormalized values, body mass normalized values, and body weight times height normalized values. Without normalization, height or weight accounted for 7-82% of the variance in all 10 peak components of the moments. With normalization, height and weight accounted for at most 6% of the variance with the exception of the hip adduction moment normalized by body weight times height and the ankle dorsiflexion moment normalized by body mass. For the hip adduction moment normalized by body weight times height, height still accounted for 13% of the variance (p<0.001) and for the ankle dorsiflexion moment normalized by body mass, 22% of the variance (p<0.001). After normalization, significant differences between males and females remained for only two out of 10 moments with the body weight times height method compared to six out of 10 moments with the body mass method. When compared to the unnormalized data, both normalization methods were highly effective in reducing height and weight differences. Even for the two cases where one normalization method was less effective than the other (hip adduction-body weight times height; ankle dorsiflexion-body mass) the normalization process reduced the variance ascribed to height or weight by 48% and 63%, respectively, as compared to the unnormalized data.

External knee adduction and flexion moments during gait and medial tibiofemoral disease progression in knee osteoarthritis

Objective Test the hypothesis that greater baseline peak external knee adduction moment (KAM), KAM impulse, and peak external knee flexion moment (KFM) during the stance phase of gait are associated with baseline-to-2-year medial tibiofemoral cartilage damage and bone marrow lesion progression, and cartilage thickness loss. Methods Participants all had knee OA in at least one knee. Baseline peak KAM, KAM impulse, and peak KFM (normalized to body weight and height) were captured and computed using a motion analysis system and 6 force plates. Participants underwent MRI of both knees at baseline and two years later. To assess the association between baseline moments and baseline-to-2-year semiquantitative cartilage damage and bone marrow lesion progression and quantitative cartilage thickness loss, we used logistic regression with generalized estimating equations (GEE), adjusting for gait speed, age, gender, disease severity, knee pain severity, and medication use. Results The sample consisted of 391 knees (204 persons): mean age 64.2 years (SD 10.0); BMI 28.4 kg/m2 (5.7); 156 (76.5%) women. Greater baseline peak KAM and KAM impulse were each associated with worsening of medial bone marrow lesions, but not cartilage damage. Higher baseline KAM impulse was associated with 2-year medial cartilage thickness loss assessed both as % loss and as a threshold of loss, whereas peak KAM was related only to % loss. There was no relationship between baseline peak KFM and any medial disease progression outcome measures. Conclusion Findings support targeting KAM parameters in an effort to delay medial OA disease progression.

Bone mineral density in the proximal tibia varies as a function of static alignment and knee adduction angular momentum in individuals with medial knee osteoarthritis

Based on the premise that bone mass and bone geometry are related to load history and that subchondral bone may play a role in osteoarthritis (OA), we sought to determine if static and dynamic markers of knee joint loads explain variance in the medial-to-lateral ratio of proximal tibial bone mineral density (BMD) in subjects with mild and moderate medial knee OA. We utilized two surrogate markers of dynamic load, the peak knee adduction moment and the knee adduction angular momentum, the latter being the time integral of the frontal plane knee joint moment. BMD for medial and lateral regions of the proximal tibial plateau and one distal region in the tibial shaft was measured in 84 symptomatic subjects with Kellgren and Lawrence radiographic OA grades of 2 or 3. Utilizing gait analysis, the peak knee adduction moment (the external adduction moment of greatest magnitude) and the time integral of the frontal plane knee joint moment (the angular momentum) over the entire stance phase as well as for each of the four subdivisions of stance were calculated. The BMD ratio was not significantly different in grade 2 (1.32 +/- 0.27) and grade 3 knees (1.47 +/- 0.40) (P = 0.215). BMD of the tibial shaft was not correlated with any loading parameter or static alignment. Of all the surrogate gait markers of dynamic load, the knee adduction angular momentum in terminal stance explained the most variance (20%) in the medial-to-lateral BMD ratio (adjusted r(2) = 0.196, P < 0.001). The knee adduction angular momentum for the entire stance phase explained 18% of the variance in the BMD ratio (adjusted r(2) = 0.178, P < 0.001), 10% more variance than explained by the overall peak knee adduction moment (adjusted r(2) = 0.081, P < 0.001). 18% of the variance in the BMD ratio was also explained by the knee alignment angle (adjusted r(2) = 0.183, P < 0.001), and the total explanatory power was increased to 22% when the knee adduction angular momentum in terminal stance was added (change in r(2) = 0.041, P < 0.05, total adjusted r(2) = 0.215, P < 0.001). The BMD ratio and its relationship to dynamic and static markers of loading were independent of height, weight, and the body mass index, demonstrating that both dynamic markers of knee loading as well as knee alignment explained variance in the tibial BMD ratio independent of body size.

Denuded Subchondral Bone and Knee Pain in Persons with Knee Osteoarthritis

OBJECTIVE It is unclear how articular cartilage loss contributes to pain in patients with knee osteoarthritis (OA). Full-thickness cartilage defects expose the subchondral bone plate. The relationship between denuded bone and pain has not been examined. The aim of this study was to investigate whether the percent of denuded bone is associated with moderate-to-severe knee pain or frequent knee pain and longitudinally with frequent knee pain 2 years after the baseline evaluation. METHODS We studied 182 persons with knee OA (305 knees). Applying specialized magnetic resonance imaging techniques, manual segmentation was used to compute cartilage-covered and denuded bone areas for each surface. Moderate-to-severe knee pain was defined as a score of >or=40 mm on a knee-specific 100-mm visual analog scale, and frequent knee pain was defined as pain on most days during the past month. Logistic regression and generalized estimating equations were used in analyses, adjusting for age, sex, body mass index, and bone marrow lesions. RESULTS Cross-sectional analyses revealed that moderate-to-severe knee pain was associated with percent denuded bone in the medial compartment (adjusted odds ratio [OR] 3.90, 95% confidence interval [95% CI] 1.33-11.47), in the medial and patellar surfaces together, and in the lateral and patellar surfaces. Frequent knee pain was associated with percent denuded bone in the patellar surface (adjusted OR 3.11, 95% CI 1.24-7.81), in the medial and patellar surfaces, and in the lateral and patellar surfaces. Longitudinal analyses (in 168 knees without frequent knee pain at baseline) revealed that percent denuded bone in the medial and patellar surfaces was associated with frequent incident knee pain (adjusted OR 4.19, 95% CI 1.56-11.22). CONCLUSION These results support a relationship between subchondral bone plate exposure and prevalent and incident knee pain in patients with knee OA.

Time course and extent of functional recovery during the first postoperative year after minimally invasive total hip arthroplasty with two different surgical approaches—a randomized controlled trial

UNLABELLED While others have reported short-term comparisons between various minimally invasive surgical (MIS) approaches to total hip arthroplasty (THA) and their conventional analogues, longer-term data is lacking, as is information indicating whether MIS approaches to THA provide a biomechanically complete recovery. Furthermore, different MIS approaches have not been compared. Our approaches of interest were a one-incision modified Watson-Jones, and a two-incision approach. HYPOTHESES (1) There are significant differences in gait recovery patterns between the two surgical groups and (2) THA subjects have significant differences in function one year after surgery compared to control subjects. To test these hypotheses, THA candidates (n=26) were randomized to receive one of these MIS approaches and evaluated preoperatively, and postoperatively at 3 weeks, and at 3, 6 and 12 months. Evaluations included three-dimensional gait analysis and 24-hour step-counts. The same data were obtained from 25 control subjects. Recovery time-course was assessed using repeated measures ANOVA. T-tests were used to compare controls with the pooled group of THA subjects. We found no differences between the two THA surgical groups regarding the time-course of recovery (p≥0.591). Although recovery was statistically complete by 3 months postoperatively for all variables, there were significant differences from controls at 12 months. Most notably, the external hip adduction moment, which reflects hip abductor function, was more than one standard deviation below normal (p<0.001). THA subject inactivity could not explain the gait differences, since one year after surgery daily step counts were not significantly different from controls (p=0.346). More work is necessary to determine ways to improve biomechanical outcomes for todays patients with high expectations for function and implant longevity.

Subregional effects of meniscal tears on cartilage loss over 2 years in knee osteoarthritis

Objectives Meniscal tears have been linked to knee osteoarthritis progression, presumably by impaired load attenuation. How meniscal tears affect osteoarthritis is unclear; subregional examination may help to elucidate whether the impact is local. This study examined the association between a tear within a specific meniscal segment and subsequent 2-year cartilage loss in subregions that the torn segment overlies. Methods Participants with knee osteoarthritis underwent bilateral knee MRI at baseline and 2 years. Mean cartilage thickness within each subregion was quantified. Logistic regression with generalised estimating equations were used to analyse the relationship between baseline meniscal tear in each segment and baseline to 2-year cartilage loss in each subregion, adjusting for age, gender, body mass index, tear in the other two segments and extrusion. Results 261 knees were studied in 159 individuals. Medial meniscal body tear was associated with cartilage loss in external subregions and in central and anterior tibial subregions, and posterior horn tear specifically with posterior tibial subregion loss; these relationships were independent of tears in the other segments and persisted in tibial subregions after adjustment for extrusion. Lateral meniscal body and posterior horn tear were also associated with cartilage loss in underlying subregions but not after adjustment for extrusion. Cartilage loss in the internal subregions, not covered by the menisci, was not associated with meniscal tear in any segment. Conclusion These results suggest that the detrimental effect of meniscal tears is not spatially uniform across the tibial and femoral cartilage surfaces and that some of the effect is experienced locally.

Knee confidence as it relates to physical function outcome in persons with or at high risk of knee osteoarthritis in the osteoarthritis initiative.

OBJECTIVE To evaluate whether low knee confidence at baseline is associated with poor baseline-to-3-year physical function outcome in the Osteoarthritis Initiative. METHODS Knee confidence was assessed using an item from the Knee Injury and Osteoarthritis Outcome Score instrument. Physical function was assessed using self-report measures (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC] function score and Short Form 12 physical component scale) and performance-based measures (20-meter walk and chair stand test). Poor function outcome was defined as moving into a worse function group or remaining in the 2 worst function groups between baseline and 3 years. Logistic regression was used to evaluate the relationship between baseline knee confidence level and poor baseline-to-3-year function outcome, adjusting for potential confounders. RESULTS The sample included 3,975 men and women with or at high risk of developing osteoarthritis of the knee, of whom 37-53% had poor baseline-to-3-year function outcome. For both self-report measures, increasingly worse knee confidence was associated with a greater risk of poor function outcome, and trend tests supported a graded response (e.g., the adjusted odds ratios [95% confidence intervals] for the WOMAC function score for worsening confidence categories were 1.26 [1.07-1.49], 1.43 [1.16-1.77], and 2.05 [1.49-2.82], P for trend <0.0001). Similar associations between confidence and performance-based function outcome were observed, but statistical significance did not persist in adjusted analyses. Factors independently associated with poor function outcome for all 4 outcome measures were depressive symptoms, comorbidity, body mass index, and joint space narrowing. CONCLUSION These findings indicate that worse knee confidence at baseline is independently associated with greater risk of poor function outcome by self-report measures, with evidence of a graded response; the relationship with performance measures is not significant in fully adjusted models.

Varus-valgus alignment: reduced risk of subsequent cartilage loss in the less loaded compartment.

OBJECTIVE Varus-valgus alignment has been linked to subsequent progression of osteoarthritis (OA) within the mechanically stressed (medial for varus, lateral for valgus) tibiofemoral compartment. Cartilage data from the off-loaded compartment are sparse. The purpose of this study was to examine our hypotheses that neutral and valgus (versus varus) knees each have reduced odds of cartilage loss in the medial subregions and that neutral and varus (versus valgus) knees each have reduced odds of cartilage loss in the lateral subregions. METHODS Patients with knee OA underwent knee magnetic resonance imaging at baseline and 2 years. The mean cartilage thickness was quantified within 5 tibial and 3 femoral subregions. We used logistic regression with generalized estimating equations to analyze the relationship between baseline alignment and subregional cartilage loss at 2 years, adjusting for age, sex, body mass index, and disease severity. RESULTS A reduced risk of cartilage loss in the medial subregions was associated with neutral (versus varus) alignment (external tibial, central femoral, external femoral) and with valgus (versus varus) alignment (central tibial, external tibial, central femoral, external femoral). A reduced risk of cartilage loss in the lateral subregions was associated with neutral (versus valgus) alignment (central tibial, internal tibial, posterior tibial) and with varus (versus valgus) alignment (central tibial, external tibial, posterior tibial, external femoral). CONCLUSION Neutral and valgus alignment were each associated with a reduction in the risk of subsequent cartilage loss in certain medial subregions and neutral and varus alignment with a reduction in the risk of cartilage loss in certain lateral subregions. These results support load redistribution as an in vivo mechanism of the long-term alignment effects on cartilage loss in knee OA.

Factors Associated With Pain Experience Outcome in Knee Osteoarthritis

Few strategies to improve pain outcome in knee osteoarthritis (OA) exist in part because how best to evaluate pain over the long term is unclear. Our objectives were to determine the frequency of a good pain experience outcome based on previously formulated OA pain stages and test the hypothesis that less depression and pain catastrophizing and greater self‐efficacy and social support are each associated with greater likelihood of a good outcome.

Knee Instability and Basic and Advanced Function Decline in Knee Osteoarthritis

Manifestations of instability in knee osteoarthritis (OA) include low overall knee confidence, low confidence that the knees will not buckle, buckling, and excessive motion during gait. Confidence and buckling may particularly influence activity choices, contributing to events leading to disability. Buckling is more likely to affect advanced than basic functional tasks. In this prospective longitudinal study, we tested the hypothesis that overall knee confidence, buckling confidence, buckling, and frontal plane motion during gait are associated with advanced 2‐year function outcomes in persons with knee OA.