Self-reported knee joint instability is related to passive mechanical stiffness in medial knee osteoarthritis.

BACKGROUND: Self-reported knee joint instability compromises function in individuals with medial knee osteoarthritis and may be related to impaired joint mechanics. The purpose of this study was to evaluate the relationship between self-reported instability and the passive varus-valgus mechanical behaviour of the medial osteoarthritis knee. METHODS: Passive varus-valgus angular laxity and stiffness were assessed using a modified isokinetic dynamometer in 73 participants with medial tibiofemoral osteoarthritis. All participants self-reported the absence or presence of knee instability symptoms and the degree to which instability affected daily activity on a 6-point likert scale. RESULTS: Forward linear regression modelling identified a significant inverse relationship between passive mid-range knee stiffness and symptoms of knee instability (r = 0.27; P < 0.05): reduced stiffness was indicative of more severe instability symptoms. Angular laxity and end-range stiffness were not related to instability symptoms (P > 0.05). CONCLUSIONS: Conceivably, a stiffer passive system may contribute toward greater joint stability during functional activities. Importantly however, net joint stiffness is influenced by both active and passive stiffness, and thus the active neuromuscular system may compensate for reduced passive stiffness in order to maintain joint stability. Future work is merited to examine the role of active stiffness in symptomatic joint stability.

Reliability, Validity, Responsiveness, and Minimum Important Change of the Stair Climb Test in Adults With Hip and Knee Osteoarthritis.

OBJECTIVE: The Osteoarthritis Research Society International (OARSI) recommends assessment of physical function using a performance-based test of stair negotiation but was unable to recommend any specific test. We assessed the reliability, validity, responsiveness, measurement error, and minimum important change (MIC) of the 6-step timed Stair Climb Test (SCT). METHODS: We used pooled data from 397 participants with hip or knee osteoarthritis (54% women) from 4 clinical trials (86% retained at 12-week follow-up). Construct validity was assessed by testing 6 a priori hypotheses against other OARSI-recommended physical function measures. A self-reported Global Rating of Change scale was used to classify participants as worsened, improved, and stable. Participants who worsened in physical function were excluded from all analyses. Responsiveness and MIC were assessed using multiple anchor-based and distribution-based approaches. Test-retest reliability, standard error of measurement (SEM), and smallest detectable change (SDC) were assessed on stable participants. RESULTS: Five of 6 hypotheses (83%) for construct validity were met. Test-retest reliability was excellent (intraclass correlation coefficient2,1 0.83; 95% confidence interval 0.71-0.90). The SEM and SDC values were 0.44 and 1.21 seconds, respectively. We did not find adequate support for responsiveness. The MIC values ranged from 0.78 to 1.95 seconds using different approaches (median 1.37 seconds). CONCLUSION: The 6-step timed SCT adequately assesses the construct of physical function in individuals with hip or knee osteoarthritis with excellent 12-week test-retest reliability. However, support for its responsiveness was inadequate to recommend its use as an outcome measure in people with osteoarthritis for research and clinical practice.

Muscle and exercise in the prevention and management of knee osteoarthritis: an internal medicine specialist's guide.

This article outlines the influence of muscle activity on knee-joint loading, describes the deficits in muscle function observed in people with knee osteoarthritis, and summarizes available evidence pertaining to the role of muscle in the development and progression of knee osteoarthritis. The article focuses on whether muscle deficits can be modified in knee osteoarthritis and whether improvements in muscle function lead to improved symptoms and joint structure. This article concludes with a discussion of exercise prescription for muscle rehabilitation in knee osteoarthritis.

Impact loading following quadriceps strength training in individuals with medial knee osteoarthritis and varus alignment.

BACKGROUND: Greater impact loading at initial contact is postulated to play a role in the progression of osteoarthritis. Quadriceps weakness is common in individuals with knee osteoarthritis and may contribute to high impact loading. The purpose of this study was to examine the effects of quadriceps strengthening on impact loading parameters. METHODS: Data from 97 individuals with knee osteoarthritis who participated in a randomized clinical trial examining effects of a 12-week quadriceps strengthening program was used to conduct this secondary exploratory analysis. Participants completed a three-dimensional gait assessment within 10% of 1.0m/s from which maximum rate of loading (Body Weight/second), average rate of loading (Body Weight/second), and peak vertical ground reaction force during early stance (Body Weight) were determined. Peak isometric quadriceps strength (Nm/kg) was also assessed. FINDINGS: There was a significant increase in quadriceps strength in the training group (mean change (95%CI): 0.35(0.25, 0.045) Nm/kg, P=0.01) with no change in the control group (mean change (95%CI): 0.03(-0.39, 0.45) Nm/kg, P>0.05). There were no changes in impact loading variables. With data from both groups combined, changes in quadriceps strength explained 3% of variance in the change in maximum rate of loading. Change in quadriceps strength was not predictive of the change in peak vertical ground reaction force or average rate of loading. INTERPRETATIONS: While change in strength was predictive of change in maximal loading rate, this explained only a small proportion of the variance. Future research examining the role parameters such as neuromuscular control play in impact loading are warranted.

Update on the role of muscle in the genesis and management of knee osteoarthritis.

This updated review outlines the influence of muscle activity on knee joint loading, describes the deficits in muscle function observed in people with knee osteoarthritis, and summarizes available evidence pertaining to the role of muscle in the development and progression of knee osteoarthritis. The review also focuses on whether muscle deficits can be modified in knee osteoarthritis and whether improvements in muscle function lead to improved symptoms and joint structure. The review concludes with a discussion of exercise prescription for muscle rehabilitation in knee osteoarthritis.

Varus-valgus laxity and passive stiffness in medial knee osteoarthritis.

OBJECTIVE: To compare differences in knee varus and valgus angular laxity and passive mechanical stiffness between asymptomatic knees and those with mild, moderate, and severe knee osteoarthritis (OA). METHODS: A total of 127 participants with symptomatic medial tibiofemoral OA and 32 asymptomatic controls participated. OA knees were stratified according to radiographic severity. Varus-valgus laxity was evaluated using a customized dynamometer, providing continuous measurement of varus-valgus joint angle and torque. The following indices were calculated: 1) varus, valgus, and total angular laxity, 2) end-range varus and valgus stiffness, and 3) midrange stiffness. RESULTS: There was no difference in varus, valgus, and total angular laxity, or varus and valgus end-range stiffness between the groups (P > 0.05 for all). The OA groups were less stiff in the midrange compared with the controls (P = 0.004-0.043). CONCLUSION: The absence of differences in total angular laxity is contrary to previous findings, and may be associated with the failure of previous work to account for body size effects. Less midrange stiffness in OA participants compared with controls may indicate less rotational support provided by passive joint structures in knee OA within the functionally important range. The role of passive varus-valgus stiffness in disease onset and progression is worthy of further investigation.

Quadriceps strength is not related to gait impact loading in knee osteoarthritis.

Joint loading has been implicated in the pathogenesis of knee osteoarthritis (OA). While compartment-specific measures such as the knee adduction moment have received much attention in the literature, less is known about other measures of dynamic loading in this patient population. This cross-sectional study assessed strength and walking patterns of 204 individuals with radiographically confirmed medial tibiofemoral OA and varus malalignment. Pearson product moment correlations and regression analyses were used to determine the bivariate and multivariate relationships amongst measures of impact loading (rate of loading and heelstrike transient occurrence) with demographic, clinical (in particular, radiographic disease severity, lower limb alignment, and self-reported pain and function), and biomechanical variables (maximum voluntary isometric quadriceps strength and gait kinematics). While maximum voluntary isometric quadriceps strength was significantly correlated with rate of loading (r>0.27) when walking at a freely chosen speed, multiple regression analyses indicated that rate of loading was primarily dictated by walking speed (p<0.001), and the effect of quadriceps strength was insignificant when accounting for all other included variables. Individuals who exhibited a heelstrike transient in their vertical ground reaction force profile were significantly more varus malaligned and were more likely to demonstrate severe radiographic degeneration than those who did not exhibit heelstrike transients. These results demonstrate higher impact loading during walking in those with knee OA with faster self-selected walking speeds, though the relationship with quadriceps strength is less clear. Importantly a potential association between disease characteristics, such as malalignment and disease severity, and higher impact loading was also observed.

The association of quadriceps strength with the knee adduction moment in medial knee osteoarthritis.

OBJECTIVE: To investigate the relationship between quadriceps strength and the peak knee adduction moment during walking in medial tibiofemoral osteoarthritis (OA), and whether varus malalignment influences this relationship. METHODS: Maximum isometric quadriceps strength at 60 degrees flexion relative to body mass and the peak knee adduction moment during walking were assessed in 184 community volunteers with medial knee OA. Mechanical knee alignment was determined either directly from full-leg radiograph or extrapolated from anatomic alignment on knee radiograph using regression equations. Pearson's correlation coefficient was used to assess the association between quadriceps strength and peak knee adduction moment. The independent relationship between quadriceps strength and peak knee adduction moment, and the impact of varus malalignment on this relationship, was assessed using multiple regression analyses with and without adjustment for covariates. RESULTS: Quadriceps strength was not significantly associated with peak knee adduction moment (r = 0.14, P = 0.059). Neither quadriceps strength (b = 0.25, P = 0.142) nor the interaction between quadriceps strength and varus malalignment (b = -0.01, P = 0.693) significantly contributed to the variance in peak knee adduction moment. Results were unchanged with the inclusion of covariates. CONCLUSION: No significant association was observed between quadriceps strength and the peak knee adduction moment, and the severity of varus malalignment did not influence the relationship. Results suggest that clinicians should not be concerned that patients with knee OA and stronger quadriceps are more likely to demonstrate a higher knee adduction moment.

Does knee malalignment mediate the effects of quadriceps strengthening on knee adduction moment, pain, and function in medial knee osteoarthritis? A randomized controlled trial.

OBJECTIVE: To examine whether the effects of 12 weeks of quadriceps strengthening on the knee adduction moment, pain, and function in people with medial knee osteoarthritis (OA) differ in those with and without varus malalignment. METHODS: A single-blind, randomized controlled trial of 107 community volunteers with medial knee OA was conducted. Participants were stratified according to knee malalignment (more varus or more neutral) and then randomized into either a 12-week supervised home-based quadriceps strengthening group or a control group with no intervention. The primary outcome was the knee adduction moment, measured using 3-dimensional gait analysis. Secondary outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index scores (measuring pain and physical function), step test score, stair climb test score, and maximum quadriceps isometric strength. Analyses of covariance were carried out based on intent-to-treat principles. RESULTS: Quadriceps strengthening did not significantly alter the knee adduction moment in either the more malaligned or the more neutral group (unadjusted knee adduction moment 0.12 and 0.05% Nm/BWxHT, respectively). Function did not improve significantly following quadriceps strengthening in either alignment group, but there was a significant improvement in knee pain in the more neutrally aligned group (P < 0.001). CONCLUSION: Quadriceps strengthening did not have any significant effect on the knee adduction moment in participants with either more varus or more neutral alignment. The benefits of quadriceps strengthening on pain were more evident in those with more neutral alignment. Knee alignment thus represents a local mechanical factor that can mediate symptomatic outcome from exercise interventions in knee OA.

Varus malalignment and its association with impairments and functional limitations in medial knee osteoarthritis.

OBJECTIVE: To examine the association of varus malalignment with impairments and functional limitations in people with medial knee osteoarthritis (OA). METHODS: Anatomic radiographic knee alignment was assessed in 107 community volunteers with medial tibiofemoral knee OA. Impairments assessed included pain (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]), quadriceps and hamstring isometric strength, and knee varus-valgus laxity. WOMAC, walking speed, step test, and stair climb test were used to assess functional limitations. Participants were categorized into tertiles according to knee alignment (least, moderate, and most varus). Impairments and functional limitations between groups were compared using analyses of variance with and without adjustment for age, sex, and disease severity. Regression analyses were also performed in the entire cohort to further determine the relationship of varus malalignment to impairments and functional limitations. RESULTS: The most varus group (mean varus 7.7 degrees) did not demonstrate greater impairments or worse functional limitations compared with the moderate varus (4.2 degrees) and least varus (5.0 degrees) groups. In fact, the most varus participants performed significantly better on the step test compared with moderate (P = 0.006) and least varus (P = 0.004) participants. Knee alignment accounted for a significant but small proportion of the variance in step test performance (7%) and quadriceps strength (4%), but did not contribute significantly to the variance in any other parameter measured. CONCLUSION: Greater varus malalignment was associated with increased quadriceps strength and improved step test performance, but did not influence the severity of other measured impairments and functional limitations.

Role of muscle in the genesis and management of knee osteoarthritis.

The muscles of the lower limb play an important role in the genesis and management of knee osteoarthritis (OA). This article outlines the influence of muscle activity on knee joint loading, the deficits in muscle function observed in people who have knee OA, and available evidence pertaining to the role of muscle in the development and progression of knee OA. It also discusses whether muscle deficits can be modified in knee OA and whether improvements in muscle function lead to improved symptoms and joint structure. It concludes with a discussion of exercise prescription for muscle rehabilitation in knee OA.