Alison H. Chang

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.

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.

Overweight: advancing our understanding of its impact on the knee and the hip

Why the effect of excess body weight is greater at the knee In their study, Reijman et al 1 (see page 158) report findings that show an association between an increased body mass index (BMI) and greater risk of both incident knee osteoarthritis and knee osteoarthritis progression, but no association between an increased BMI and risk of either incident or progressive hip osteoarthritis. These results confirm what previous studies—that is, studies that were not specifically designed to look at the effect of BMI on the knee and the hip—had hinted at, that BMI has no effect or a smaller effect at the hip than at the knee. As the first study in which BMI effects on the knee and hip were examined in the same population, the study by Reijman et al is a landmark study. In the literature, summarised by Reijman et al 1 in this issue of the journal, the evidence supporting a BMI effect on risk of incident knee osteoarthritis is strong, particularly in women. For example, in a longitudinal study of the Chingford population (women, mean age 54 years), belonging to the top BMI tertile was associated with an increased risk of knee osteoarthritis (odds ratio (OR) 2.38, 95% confidence interval (CI) 1.29 to 4.39) in adjusted analyses.2 In Framingham participants, higher BMI increased the risk of knee osteoarthritis (OR 1.6/5 unit increase, 95% CI 1.2 to 2.2), as did increase in weight (OR 1.4/10 lb increase in weight).3 Findings were confirmed in women but not men perhaps because of the smaller number of incident cases in men. By contrast, several studies, as noted by Reijman et al ,1 have not detected any influence or only a modest effect of BMI on knee osteoarthritis progression, whereas they did disclose other risk factors for …

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.

In vivo and noninvasive six degrees of freedom patellar tracking during voluntary knee movement

OBJECTIVE The purpose of this study was to investigate in vivo and noninvasively patellar tracking in six degrees of freedom during voluntary knee extension and flexion. DESIGN Patellar tracking was evaluated in vivo and noninvasively with corroboration using in vivo fluoroscopy and in vitro cadaver measurements. BACKGROUND Patellofemoral pain is closely related to abnormal patellar tracking and malalignment. However, there is a lack of quantitative and convenient methods to evaluate six degrees of freedom in vivo patellar tracking, partly due to difficulty in evaluating 3-D patellar tracking noninvasively. METHODS Six degrees of freedom patellar tracking was measured in vivo and noninvasively using a small clamp mounted onto the patella and an optoelectronic motion capture system in 18 knees of 12 healthy subjects during voluntary knee extension and flexion. RESULTS The patella tracked systematically following a certain pattern during knee extension and flexion. Patellar tracking patterns during knee extension and flexion were not significantly different in the 18 knees tested. When the knee was voluntarily extended from 15 degrees flexion to full extension, the patella was extended 8 degrees, laterally tilted 2 degrees, and shifted 3 mm laterally and 10 mm proximally. The results were consistent with previous in vitro and in vivo studies. CONCLUSION Six degrees of freedom patellar tracking can be evaluated in vivo and noninvasively within the range of 20 degrees flexion to full knee extension. RELEVANCE The study provided us quantitative six degrees of freedom information about patellar tracking during knee flexion/extension, which can be used to investigate patellar tracking in vivo and noninvasively in both healthy subjects and patients with patellofemoral disorder and patellar malalignment.

Impaired varus–valgus proprioception and neuromuscular stabilization in medial knee osteoarthritis

Impaired proprioception and poor muscular stabilization in the frontal plane may lead to knee instability during functional activities, a common complaint in persons with knee osteoarthritis (KOA). Understanding these frontal plane neuromechanical properties in KOA will help elucidate the factors contributing to knee instability and aid in the development of targeted intervention strategies. The objectives of the study were to compare knee varus-valgus proprioception, isometric muscle strength, and active muscular contribution to stability between persons with medial KOA and healthy controls. We evaluated knee frontal plane neuromechanical parameters in 14 participants with medial KOA and 14 age- and gender-matched controls, using a joint driving device (JDD) with a customized motor and a 6-axis force sensor. Analysis of covariance with BMI as a covariate was used to test the differences in varus-valgus neuromechanical parameters between these two groups. The KOA group had impaired varus proprioception acuity (1.08±0.59° vs. 0.69±0.49°, p<0.05), decreased normalized varus muscle strength (1.31±0.75% vs. 1.79±0.84% body weight, p<0.05), a trend toward decreased valgus strength (1.29±0.67% vs. 1.88±0.99%, p=0.054), and impaired ability to actively stabilize the knee in the frontal plane during external perturbation (4.67±2.86 vs. 8.26±5.95 Nm/degree, p<0.05). The knee frontal plane sensorimotor control system is compromised in persons with medial KOA. Our findings suggest varus-valgus control deficits in both the afferent input (proprioceptive acuity) and muscular effectors (muscle strength and capacity to stabilize the joint).

Effects of femoral rotational taping on pain, lower extremity kinematics, and muscle activation in female patients with patellofemoral pain

OBJECTIVES To explore the hip and knee joint kinematics as well as muscle activation between participants with patellofemoral pain syndrome (PFPS) and controls, and to investigate the immediate effect of proximal femoral rotational taping on pain, joint kinematics, and muscle activation during single-leg squat (SLS). DESIGN Cross-sectional study. METHODS Sixteen female participants with PFPS, and eight healthy female controls participated. Three-dimensional hip and patellar kinematics measured by electromagnetic tracking system, hip (gluteus maximus and gluteus medius) and thigh (rectus femoris) muscle activation measured by EMG, and subjective report of pain were recorded during SLS in three randomized conditions of no tape, sham taping, and femoral rotational taping with kinesiotape. RESULTS Without taping, compared with controls, PFPS group had increased hip adduction angle (23.5±11.3° vs. 15.8±7.3°) during SLS. Additionally, PFPS group exhibited lesser rectus femoris activity during the initial 0-15° of SLS. Application of both femoral rotational and sham tapes reduced pain for PFPS group. Compared with no tape or sham tape, femoral rotational tape significantly shifted the patella into more posterior (1.59±0.83cm in no tape vs. 1.54±0.87cm in sham tape vs. 1.32±0.72cm in femoral rotational tape) and distal (-2.49±0.95cm vs. -2.64±0.80cm vs. -3.11±0.77cm) positions in the PFPS group. CONCLUSIONS Femoral rotational taping could alter patellofemoral kinematics and decrease pain in treatment of young female participants with PFPS.

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.