Monica R. Maly

Static and dynamic biomechanics of foot orthoses in people with medial compartment knee osteoarthritis.

OBJECTIVE Gait biomechanics (knee adduction moment, center of pressure) and static alignment were investigated to determine the mechanical effect of foot orthoses in people with medial compartment knee osteoarthritis. DESIGN Repeated measures design in which subjects were exposed to three conditions (normal footwear, heel wedge and orthosis) in random order. BACKGROUND The knee adduction moment is an indirect measure of medial compartment loading. It was hypothesized that the use of a 5 degrees valgus wedge and 5 degrees valgus modified orthosis would shift the center of pressure laterally during walking, thereby decreasing the adduction moment arm and the adduction moment. METHODS Peak knee adduction moment and center of pressure excursion were obtained in nine subjects with medial compartment knee OA during level walking using an optoelectric system and force plate. Static radiographs were taken in 12 subjects using precision radiographs. RESULTS There was no difference between conditions in static alignment, the peak adduction moment or excursion of the center of pressure in the medial-lateral direction. No relationship was found between the adduction moment and center of pressure excursion in the medial-lateral plane. The displacement of the center of pressure in the anterior-posterior direction, measured relative to the laboratory coordinate system, was decreased with the orthosis compared to the control condition (P=0.036) and this measure was correlated with the adduction moment (r=0.45, P=0.019). CONCLUSIONS The proposed mechanism was not supported by the findings. The reduction in the center of pressure excursion in the anterior-posterior direction suggests that foot positioning was altered, possibly to a toe-out position, while subjects wore the orthoses. Based on the current findings, we hypothesize that toe-out positioning may reduce medial joint load. RELEVANCE Knee Osteoarthritis is the most common cause of chronic disability amongst seniors. Developing inexpensive, non-invasive treatment strategies for this large population has potential to impact health care costs, quality of life and clinical outcomes.

‘Getting back to real living’: a qualitative study of the process of community reintegration after stroke

Objectives: To examine the process of community reintegration over the first year following stroke, from the patient’s perspective. Design: Qualitative, longitudinal, grounded theory study involving ten participants. During the first year post discharge from inpatient rehabilitation, 46 one-on-one semi-structured interviews were conducted with ten participants. Interviews were completed with participants before discharge from inpatient stroke rehabilitation and in their homes at two weeks, three months, six months and one year post discharge. Analysis was guided by grounded theory methods described by Corbin and Strauss. Subjects: Four women and six men (mean age 59.6 ± 18.0, all with left hemiparesis and without aphasia) who had sustained their first hemispheric stroke and were returning to the community following inpatient rehabilitation. Results: The process of community reintegration after stroke involved transitioning through a series of goals: gaining physical function, establishing independence, adjusting expectations and getting back to real living. The ultimate challenge for stroke survivors during this process of community reintegration was to create a balance between their expectations of themselves and their physical capacity to engage in meaningful roles. Conclusions: Over the first year after stroke, participants reported that the process of community reintegration was marked by ongoing changes in their goals. Formal and informal caregivers need to work with stroke survivors living in the community to facilitate realistic and achievable goal setting. Tools which identify meaningful activities should also be incorporated to provide stroke survivors with the opportunity to contribute and engage with others in the community.

Valproate-mediated disturbances of hemostasis : relationship to dose and plasma concentration

Valproic acid (VPA) may cause impaired platelet function, thrombocytopenia and, occasionally, severe bleeding. Controversy exists both as to the mechanism of this alteration in hemostasis and as to whether these adverse effects are either dose-related or idiosyncratic. Previous investigations have focused primarily on pediatric patients who commonly were receiving multiple anticonvulsant medications. We evaluated a cohort of 27 adult patients with epilepsy who were receiving VPA monotherapy and compared them with age-matched controls to determine whether a correlation exists between platelet count, function, bleeding time, levels of von Willebrands factor antigen, and VPA dose or plasma concentration. VPA patients had significantly lower platelet counts and longer bleeding times than did controls (p < 0.05). Platelet count was inversely correlated to VPA dose and both free and total VPA concentration (p < 0.01). There was no significant difference in levels of von Willebrands factor antigen between patients and controls. We assessed platelet aggregation by measurement of whole-blood platelet aggregation and release with agonists including adenosine diphosphate, thrombin, collagen, arachidonic acid, and ristocetin. VPA patients had significant decreases in platelet aggregation values compared with controls. There were significant differences in collagen, arachidonic acid, and adenosine diphosphate release and aggregation between groups that correlated to both VPA dose (p < 0.01) and concentration (p < 0.05). Prolongation of bleeding time was significantly correlated to both VPA dose and concentration. Our data suggest a significant relationship between impaired platelet function and both VPA dose and plasma concentration.

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.

Abnormal and cumulative loading in knee osteoarthritis.

PURPOSE OF REVIEW This review examines recent advances in understanding the abnormal mechanics characteristic of knee osteoarthritis and provides a rationale to assess the total exposure to knee loading during daily activity. RECENT FINDINGS The abnormal loading environment in knee osteoarthritis is represented by the knee adduction moment. While knee osteoarthritis gait research focuses on this variable, emerging evidence supports a critical role for knee kinematics, muscle activation patterns and the kinematics and kinetics of other lower extremity joints in the development and progression of this disease. Nevertheless, abnormal knee loading is not the only cause of articular cartilage disruption. Excessive and repetitive loading, together creating a total exposure to loading, are critical factors in knee pathomechanics. To assess excessive and repetitive loading, cumulative load is a biomechanical approach that integrates loading exposures to represent the accumulated load that knee tissues endure during physical activity. SUMMARY Knee osteoarthritis pathomechanics involves an interaction between abnormal and excessive and/or repetitive loading. Mechanics of lower extremity joints and muscle activation patterns influence the knee loading environment. Future work could integrate measures of abnormal loading with assessments of the total exposure to loading during physical activity to better link biomechanics with clinical outcomes in knee osteoarthritis.

Mechanical factors relate to pain in knee osteoarthritis.

BACKGROUND Pain experienced by people with knee osteoarthritis is related to psychosocial factors and damage to articular tissues and/or the pain pathway itself. Mechanical factors have been speculated to trigger this pain experience; yet mechanics have not been identified as a source of pain in this population. The purpose of this study was to identify whether mechanics could explain variance in pain intensity in people with knee osteoarthritis. METHODS Data from 53 participants with physician-diagnosed knee osteoarthritis (mean age=68.5 years; standard deviation=8.6 years) were analyzed. Pain intensity was reported on the Western Ontario and McMaster Universities Osteoarthritis Index. Mechanical measures included weight-bearing varus-valgus alignment, body mass index and isokinetic quadriceps torque. Gait analysis captured the range of adduction-abduction angle, range of flexion-extension angle and external knee adduction moment during level walking. FINDINGS Pain intensity was significantly related to the dynamic range of flexion-extension during gait and body mass index. A total of 29% of the variance in pain intensity was explained by mechanical variables. The range of flexion-extension explained 18% of variance in pain intensity. Body mass index added 11% to the model. The knee adduction moment was unrelated to pain intensity. INTERPRETATION The findings support that mechanical factors are related to knee osteoarthritis pain. Because limitations in flexion-extension range of motion and body size are modifiable factors, future research could examine whether interventions targeting these mechanics would facilitate pain management.

Personal experience of living with knee osteoarthritis among older adults

Purpose. Knee osteoarthritis (OA) is the most common cause of chronic disability amongst community-dwelling older adults. Yet, little is understood about the daily experience of knee OA. As clinicians we fail to understand a large group of individuals that we aim to help. We conducted an exploratory study that aimed to understand the experience of living with knee OA in older adults. Method. We used a descriptive phenomenology, grounded in the phenomenology in practice tradition. We conducted nine interviews with participants with physician-diagnosed knee OA, of different ages, sexes, cultural backgrounds and self-perceptions. Ninety-minute interviews with each participant were audio-taped and transcribed verbatim. We used the vanKaam method of phenomenological analysis, modified by Moustakas, as the framework for data analysis. Findings. The following five themes on living with knee OA emerged: experiencing knee pain is central to daily living, experiencing mobility limitations devalues self-worth, sharing the experience, assessing our own health and managing chronic pain. Conclusions. The implications of these findings highlight the profound impact knee OA has on daily living, which have been poorly documented in the past. Clinicians should consider that the consequences of living with knee OA are significant enough to influence a persons sense of self-worth.

Quantifying Self-Report Measures' Overestimation of Mobility Scores Postarthroplasty

Background Self-reports of function may systematically overestimate the ability of patients to move around postarthroplasty. Objective The purpose of this study was to estimate the magnitude of systematic differences in Lower Extremity Functional Scale (LEFS) and Western Ontario and McMaster Universities Osteoarthritis Index physical function subscale (WOMAC-PF) scores before and after primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) by referencing the values to Six-Minute Walk Test (6MWT) distances and Timed “Up & Go” Test (TUG) times. Design This study was a secondary analysis of data from a prospective cohort study. Methods The LEFS, WOMAC, 6MWT, and TUG were administered to 85 patients prearthroplasty and once at 9 to 13 weeks postarthroplasty. Regression analysis was applied using a robust error term for clustered data. With the self-report measures as dependent variables and performance measures, occasion (prearthroplasty or postarthroplasty), and performance measure-by-occasion as independent variables, 3 propositions were examined: (1) the relationship between self-report and performance measures is identical prearthroplasty and postarthroplasty (ie, regression lines are coincident); (2) the relationship differs between occasions, but is consistent (ie, regression lines are parallel); (3) the relationship is not consistent (ie, the regression lines are not parallel). Results For all analyses, the results supported the second proposition (ie, the relationship differed between occasions, but was consistent). The systematic differences varied by location of arthroplasty, but were similar for both performance tests. For the LEFS, the difference was approximately 11 points for patients who received TKA and 13 points for patients who received THA. For the WOMAC-PF, the difference was approximately 12 points for patients who received TKA and 19 points for patients who received THA. These differences exceed the minimal clinically important change for an individual patient. Limitations The findings are specific to 9 to 13 weeks postarthroplasty. Conclusion Dependence on scores of self-report measures alone, without knowledge of the magnitude of the identified systematic differences, will result in overestimating the ability of patients to move around postarthroplasty.

Relationship of intermuscular fat volume in the thigh with knee extensor strength and physical performance in women at risk of or with knee osteoarthritis

To determine the extent to which thigh intermuscular fat (IMF) and quadriceps muscle (QM) volumes explained variance in knee extensor strength and physical performance in women with radiographic knee osteoarthritis (ROA) and without.

Longitudinal changes in intermuscular fat volume and quadriceps muscle volume in the thighs of women with knee osteoarthritis

To quantify rates of change in quadriceps muscle (QM) and intermuscular fat (IMF) volumes over 2 years in women in the Osteoarthritis Initiative (OAI) study and examine group differences between those with radiographic osteoarthritis (ROA) and those without ROA.