Karen W. Hayes

Quadriceps strength and osteoarthritis progression in malaligned and lax knees

Context Experts routinely recommend that adults with knee osteoarthritis strengthen leg muscles. Contribution This 18-month cohort study of 237 adults with primary knee osteoarthritis found that greater baseline quadriceps strength was associated with greater risk for progressive tibiofemoral joint space narrowing among adults with malaligned or very lax knees. Implications Maximization of quadriceps strength in osteoarthritic patients with malaligned or very lax knees may not be joint protective and should be studied in trials that include joint structure outcomes. Cautions These results do not imply that physical activity in adults with knee osteoarthritis is harmful. The Editors Knee osteoarthritis is responsible for more chronic disability in elderly persons than any other medical condition (1). Quadriceps strengthening is widely recommended for knee osteoarthritis (2, 3), based on cross-sectional studies identifying strength (maximal voluntary muscle force generation) as a correlate of physical function (4-8) and on trials, predominantly short term, suggesting that quadriceps strengthening reduces pain and improves function (9, 10). The impact of quadriceps strength on the course of osteoarthritic disease itself is not well understood. A longitudinal study has shown that, in healthy knees, strong quadriceps offer some protection against new osteoarthritis development (11). However, whether quadriceps strength protects against progression or advancement of osteoarthritis in already arthritic knees has not been demonstrated. Brandt and colleagues (12) found no difference in baseline quadriceps strength between those with and those without disease progression. The effect of quadriceps strength on osteoarthritis disease progression is particularly important given the frequency with which quadriceps strengthening exercises are prescribed for persons with knee osteoarthritis. Muscle effects are less predictable in arthritic knees than in healthy knees. On the positive side, muscle activity promotes cartilage health and stabilizes the joint. During activity, muscles contract at different levels and protective reflexes are applied to shield knee tissues from injury (13). Coactivation, the dual drive of agonist and antagonist muscles, provides control for the stop and start of motion as well as compensation for gravity. Implicit in the recommendation of quadriceps strengthening for knee osteoarthritis is the assumption that greater strength will enhance these positive effects. If this enhancement comes without cost, greater strength may indeed protect arthritic joints from osteoarthritis progression. On the negative side, greater quadriceps strength may be associated with forces that could damage the vulnerable articular cartilage of osteoarthritis. The compensatory increase in muscle forces in osteoarthritis may increase the joint reaction force (14). A higher coactivation level in the agonist versus antagonist muscles can impair motion regulation and reduce ligament-protecting actions (13). The net impact of quadriceps strength on osteoarthritis progression depends on which effectspositive or negativeare greater. Which muscle effects prevail is likely to depend on the local mechanical environment. Local factors that alter load distribution, such as laxity and malalignment, influence how well the joint copes with muscle forces. Woo and associates (15) liken this situation to a hammer (muscle) driving a nail (the joint), while a hand (ligaments and, more broadly, local environment) holds the nail in place. The stabilizing hand allows greater force from the hammer. In other words, a healthy environment contributes to safe muscle force distribution over the menisci, articular cartilage, and other tissues. However, with laxity or malalignment, muscle forces may increase stress on localized areas of cartilage. Similarly, Marks and colleagues (16) theorized that local joint abnormalities can render muscle forces pathogenic. Malalignment and laxity are key local abnormalities. Any shift from a neutral hipkneeankle alignment alters load distribution; varus and valgus alignments increase medial and lateral compartment forces, respectively (17). Alignment influences the outcome of most knee surgeries, as well as natural disease progression and functional decline in osteoarthritis (18). Knee laxityabnormal displacement of the tibia with respect to the femur (19)shifts opposing surfaces of tibiofemoral contact so that congruence is reduced and increases shear and compression forces. Varusvalgus laxity has been linked to greater likelihood of osteoarthritis after ligament injury (20, 21). In other studies, laxity was present in patients with osteoarthritis before full-blown disease and was worsened by aspects of disease (22), was associated with worse function, and altered the strengthfunction relationship (23). If greater quadriceps strength improves the load imbalance created by malalignment or attenuated load in malaligned knees, it might protect against osteoarthritis progression in patients with maligned knees. Alternatively, malalignment may alter the line of action of quadriceps forces, distributing them inequitably across the joint surface (16); in this case, strength might increase the likelihood of osteoarthritis progression. In the lax knee, strength might be protective if greater quadriceps strength enhances dynamic stabilization. However, if the cost of this compensationthat is, greater joint reaction forceexceeds the stabilization benefit, the likelihood of osteoarthritis progression might increase. Our objective was to determine whether greater quadriceps strength was associated with greater probability of tibiofemoral osteoarthritis progression among all knees in persons with osteoarthritis and in two subsets, malaligned knees and high-laxity knees. Methods Participants Mechanical Factors in Arthritis of the Knee (MAK) is a natural history study of knee osteoarthritis at Northwestern University in Chicago, Illinois. Participants in MAK were recruited through periodicals targeting senior citizens, 67 neighborhood organizations, the registry of the Northwestern University Buehler Center on Aging, and medical center referrals. Inclusion and exclusion criteria were based on those developed for osteoarthritis progression studies at a workshop sponsored by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Institute on Aging (24). Inclusion criteria were definite osteophyte presence (Kellgren and Lawrence radiographic grade 2) in one or both knees and at least a little difficulty (Likert category) with at least two items in the Western Ontario and McMaster University osteoarthritis index physical function scale. Exclusion criteria were corticosteroid injection within 3 months, avascular necrosis, rheumatoid or other inflammatory arthritis, periarticular fracture, Paget disease, villonodular synovitis, joint infection, ochronosis, neuropathic arthropathy, acromegaly, hemochromatosis, Wilson disease, osteochondromatosis, gout, pseudogout, osteopetrosis, bilateral total knee replacement, or plan for knee replacement within the next year. Persons with past unilateral knee replacement were eligible if they had osteoarthritis in the nonreplaced knee. The institutional review board of Northwestern University approved the study, and all participants gave informed consent. Measurement of Key Factors All measurements were obtained in both knees. Isokinetic quadriceps strength was tested by using a computer-driven isokinetic dynamometer (Cybex, Avocent, Huntsville, Alabama) to assess maximal torque during movement. One tester assessed all participants by following a previously described protocol (23). The computer recorded data in foot-pounds (ft-lbs) and corrected for gravity effects. Reliability, determined by using test repetitions, was high (intraclass correlation coefficients > 0.98) (23). To assess alignment, a single anteroposterior radiograph of both lower extremities was obtained by using a graduated grid cassette (51 14 inches), adhering to a protocol we have described elsewhere (18). Alignment was defined as the measure of the angle formed by the intersection of the line connecting the centers of the femoral head and intercondylar notch and the line connecting the centers of the ankle talus and tibial spines (17, 25, 26). Knees were considered more neutral if the angle was less than 5 degrees in a varus or valgus direction and malaligned if the angle was 5 degrees or more. One experienced reader made all measurements. Reliability, based on a set of radiographs from patients with osteoarthritis (18), was high for varus and valgus alignment (intraclass correlation coefficients, 0.99 and 0.98, respectively). Varus-valgus laxity was measured with a device designed for the MAK study by Dr. Thomas Buchanan (22, 23). The measurement protocol has been described elsewhere (22, 23). Angular deviation was measured at the foot with application of varus or valgus load. Varusvalgus laxity was analyzed as the sum of varus and valgus rotation for each knee (27-29). Because a definition of high and low laxity is not available, knees in the highest laxity tertile ( 5.75 degrees) were designated as high laxity. Laxity measurements were performed by the same examiner and assistant, and reliability was very good in participants with osteoarthritis (within-session intraclass correlation coefficients, 0.85 to 0.96; between-sessions intraclass correlation coefficients, 0.84 to 0.90) (22). Measurement of Outcome Knee radiographs were obtained at baseline and at 18 months, following the semi-flexed, fluoroscopically confirmed protocol developed by Buckland-Wright (24, 30, 31). Knee position, beam alignment, markers to account for magnification, and measurement landmarks were specified. The standing semi-flexed position superimposes anterior and posterior medial tibial margins. Knee position was confir

Laxity in healthy and osteoarthritic knees

OBJECTIVE Although it is a cause of osteoarthritis (OA) in animal models, laxity in human knee OA has been minimally evaluated. Ligaments become more compliant with age; whether this results in clinical laxity is not clear. In theory, laxity may predispose to OA and/or result from OA. Our goals were to examine the correlation of age and sex with knee laxity in control subjects without OA, compare laxity in uninvolved knees of OA patients with that in older control knees, and examine the relationship between specific features of OA and knee laxity. METHODS We assessed varus-valgus and anteroposterior laxity in 25 young control subjects, 24 older control subjects without clinical OA, radiographic OA, or a history of knee injury, and 164 patients with knee OA as determined by the presence of definite osteophytes. A device was designed to assess varus-valgus laxity under a constant varus or valgus load while maintaining a fixed knee flexion angle and thigh and ankle immobilization. Radiographic evaluations utilized protocols addressing position, beam alignment, magnification, and landmark definition; the semiflexed position was used, with fluoroscopic confirmation. RESULTS In the controls, women had greater varus-valgus laxity than did men (3.6 degrees versus 2.7 degrees; 95% confidence interval [95% CI] of difference 0.38, 1.56; P = 0.004), and laxity correlated modestly with age (r = 0.29, P = 0.04). Varus-valgus laxity was greater in the uninvolved knees of OA patients than in older control knees (4.9 degrees versus 3.4 degrees; 95% CI of difference 0.60, 2.24; P = 0.0006). In OA patients, varus-valgus laxity increased as joint space decreased (slope -0.34; 95% CI -0.48, -0.19; P < 0.0001) and was greater in knees with than in knees without bony attrition (5.3 degrees versus 4.5 degrees; 95% CI of difference 0.32, 1.27; P = 0.001). CONCLUSION Greater varus-valgus laxity in the uninvolved knees of OA patients versus older control knees and an age-related increase in varus-valgus laxity support the concept that some portion of the increased laxity of OA may predate disease. Loss of cartilage/bone height is associated with greater varus-valgus laxity. These results raise the possibility that varus-valgus laxity may increase the risk of knee OA and cyclically contribute to progression.

Does laxity alter the relationship between strength and physical function in knee osteoarthritis

OBJECTIVE Since strengthening interventions have had a lower-than-expected impact on patient function in studies of knee osteoarthritis (OA) and it is known that laxity influences muscle activity, this study examined whether the relationship between strength and function is weaker in the presence of laxity. METHODS One hundred sixty-four patients with knee OA were studied. Knee OA was defined by the presence of definite osteophytes, and patients had to have at least a little difficulty with knee-requiring activities. Tests were performed to determine quadriceps and hamstring strength, varus-valgus laxity, functional status (Western Ontario and McMaster Universities Osteoarthritis Index Physical Functioning subscale [WOMAC-PF] and chair-stand performance), body mass index, and pain. High and low laxity groups were defined as above and below the sample median, respectively. RESULTS Strength and chair-stand rates correlated (r = 0.44 to 0.52), as did strength and the WOMAC-PF score (r = -0.21 to -0.36). In multivariate analyses, greater laxity was consistently associated with a weaker relationship between strength (quadriceps or hamstring) and physical functioning (chair-stand rate or WOMAC-PF score). CONCLUSION Varus-valgus laxity is associated with a decrease in the magnitude of the relationship between strength and physical function in knee OA. In studies examining the functional and structural consequences of resistance exercise in knee OA, stratification of analyses by varus-valgus laxity should be considered. The effect of strengthening interventions in knee OA may be enhanced by consideration of the status of the passive restraint system.

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.

Frequency of varus and valgus thrust and factors associated with thrust presence in persons with or at higher risk of developing knee osteoarthritis

OBJECTIVE Varus thrust observed during gait has been shown to be associated with a 4-fold increase in the risk of medial knee osteoarthritis (OA) progression. Valgus thrust is believed to be less common than varus thrust; the prevalence of each is uncertain. Racial differences in risk factors may help explain variations in the natural history of knee OA. We undertook this study to determine the frequency of varus and valgus thrust in African Americans and Caucasians and to identify factors associated with thrust presence. METHODS The Osteoarthritis Initiative cohort includes men and women who have knee OA or are at increased risk of developing it. Trained examiners assessed thrust presence by gait observation. Logistic regression with generalized estimating equations was used to identify factors associated with thrust presence, and odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated. RESULTS Compared with Caucasians, African Americans had lower odds of varus thrust, controlling for age, sex, body mass index (BMI), injury, surgery, disease severity, strength, pain, and alignment in persons without knee OA (adjusted OR 0.50 [95% CI 0.36, 0.72]) and in those with knee OA (adjusted OR 0.46 [95% CI 0.34, 0.61]). Also independently associated with varus thrust were age, sex, BMI, disease severity, strength, and alignment. The odds of valgus thrust were greater for African Americans than for Caucasians in persons without knee OA (adjusted OR 1.69 [95% CI 1.02, 2.80]) and in those with knee OA (adjusted OR 1.98 [95% CI 1.35, 2.91]). Also independently associated with valgus thrust were disease severity and malalignment. CONCLUSION Compared with Caucasians, African Americans had lower odds of varus thrust and greater odds of valgus thrust. These findings may help explain the difference between these groups in the pattern of OA involvement at the knee.

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.

Excess body weight and four-year function outcomes: comparison of African Americans and whites in a prospective study of osteoarthritis.

We evaluated whether African Americans in the Osteoarthritis Initiative (OAI) have a greater risk (versus whites) of poor 4‐year function outcome within strata defined by sex, body mass index (BMI), and waist circumference.

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.

2010 Pauline Cerasoli Lecture: Rhetoric and Responsibility in Physical Therapy Education

INTRODUCTION I want to thank the Awards Committee and Education Section for this tremendous honor. I am truly humbled to have been recognized in this way. And I want to thank Pollys family for establishing this lectureship. I knew Polly only a little, but I respected her wisdom a lot. When I was informed of this lectureship, I was told to talk about anything I wanted related to professional education, so I decided that I would like to be a bit heretical. Early in my research career, I published papers that challenged some of our cherished clinical beliefs. Today, I would like to reflect a bit on some of our cherished educational beliefs. For some time, I have been struggling with the popular concept of student-centered learning and whether an inaccurate understanding of such a model could actually encourage inappropriate student behavior. This lectureship offers me an opportunity to try to get those thoughts to coalesce and to talk about some of the challenges our educational methods pose as we prepare our future colleagues. Let me say at the start that I do not mean to disavow student-centered learning, which is well supported by research. GOALS FOR STUDENT LEARNING Based on APTAs Core Values,1 Vision 2020,2 and the Generic Abilities,3 1 think we would agree that our goals for our students include some of those listed in Table 1, which is not an exhaustive list. We all want our students to develop the background knowledge and skills to be scholarly practitioners. We want them to use the best evidence available to strive to achieve the most positive patient outcomes.4 We want them to be prepared for lifelong learning and professional development.5 In addition, we want them to understand the culture of the profession and practice in a manner that upholds it. As part of the professional culture, we expect certain professional behaviors1,5,6 that reflect the core values of our profession1 as well as respectful interaction with others,6 critical thinking,5 critical self reflection,7,8 and personal balance.5 These goals will be difficult to achieve if students are not exposed to learning environments in which they have the opportunity and latitude to develop them. The studentcentered learning model is a popular effort to provide such a learning environment. This model is somewhat broader than student-directed learning or student-regulated learning, which I believe are included within student-centered learning. So, although there are some differences between these various models, I will refer to the more global model as student-centered learning. DEFINITION OF STUDENT-CENTERED LEARNING Beginning with the learning theory behind student-centered learning, constructivism9 is learner-centered, and, according to Baviskar and colleagues,10 there are 4 essential elements. First, knowledge is constructed based on existing mental models or prior knowledge. Second, these existing mental models are challenged by new information that creates a cognitive dissonance and stimulates learners to construct new mental models.10 The new knowledge is connected in the brain to the existing knowledge, not simply stored.11 The third element is that the new learning must then be applied, with feedback If students do not actually use information, they cannot remember it They learn to use information by trying to solve problems about which they care.11 Finally, there must be reflection on the learning process.10 Student-centered learning as a curricular model has grown out of constructivism. There are many definitions of student-centered learning, but they all have some common themes. First, it is learner-centered, as distinguished from teacher-centered. In teacher-centered models, the teacher is the sage on the stage, and student learning is assumed. Teachers have no sense of variation among students. Student failures are attributed to lack of motivation, attention, or ability.12 In contrast, in student-centered learning, it is the responsibility of the student to learn. …