Exploring the relationship between pain intensity and knee moments in participants with medial knee osteoarthritis: a cross-sectional study

Background High biomechanical loading is believed to be a risk factor to pain in people with knee osteoarthritis (OA), but controversial findings have been reported on the relationship between external knee adduction moment (KAM) and pain. A more comprehensive analysis considering other factor such as external knee flexion moment (KFM) could help better reveal this relationship. This study explored the relationship between external knee adduction moment and pain intensity in participants with knee osteoarthritis (OA) using an integrated path analysis model. Methods This was a cross-sectional study based on laboratory setting. Forty-seven participants with clinical and radiographic medial knee OA were analyzed for their external knee adduction moment (KAM) and knee flexion moment (KFM) during walking using a motion analysis system. Pain intensity was measured by visual analogue scale (VAS) and the pain subscale of the Knee Injury and Osteoarthritis Outcome Score. Varus/valgus alignment was captured and quantified using a bi-planar X-ray system. Using a path analysis model, the relationships between pain intensity, KAM, KFM, OA radiographic severity, knee varus angle and walking speed were examined. Results The proposed path model met the goodness-of-fit criteria. Based on this model, KAM had a negative effect on VAS pain indirectly through the mediation of KFM. The model indicated KAM and KFM were negatively related to one another; and KFM was positively related to VAS. The KAM index, defined as (KAM/ (KAM + KFM)), was negatively related to VAS. Conclusions Path analysis enabled the construction of a more integrated pathokinematic framework for people with knee OA. The KAM index which reflected the load sharing on the frontal and sagittal planes also revealed its relationship with pain. Re-distribution of mechanical loading from frontal to sagittal plane might be a strategy for pain avoidance associated with mechanical irritation.

Estimation of the External Knee Adduction Moment during Gait Using an Inertial Measurement Unit in Patients with Knee Osteoarthritis

Although the external knee adduction moment (KAM) during gait was shown to be a quantitative parameter of medial knee osteoarthritis (OA), it requires expensive equipment and a dedicated large space to measure. Therefore, it becomes a major reason to limit KAM measurement in a clinical environment. The purpose of this study was to estimate KAM using a single inertial measurement unit (IMU) during gait in patients with knee OA. A total of 22 medial knee OA patients (44 knee joints) performed conventional gait analysis using three-dimensional (3D) motion capture system. At the same time, we attached commercial IMUs to six body segments (sternum, pelvis, both thighs, and both shanks), and IMU signals during gait were recorded synchronized with the motion capture system. The peak-to-peak difference of acceleration in the lateral/medial axis immediately after heel contact was defined as the thrust acceleration (TA). We hypothesized that TA would represent the lateral thrust of the knee during the stance phase and correlate with the first peak of KAM. The relationship between the peak KAM and TA of pelvis (R = 0.52, p < 0.001), shanks (R = 0.57, p < 0.001) and thighs (R = 0.49, p = 0.001) showed a significant correlation. The root mean square error (RMSE) of linear regression models of pelvis, shanks, and thighs to estimate KAM were 0.082, 0.079, and 0.084 Nm/(kg·m), respectively. Our newly established parameter TA showed a moderate correlation with conventional KAM. The current study confirmed our hypothesis that a single IMU would predict conventional KAM during gait. Since KAM is known as an indicator for prognosis and severity of knee OA, this new parameter has the potential to become an accessible predictor for medial knee OA instead of KAM.

Knee Joint Load Reduction by using Lateral Wedge Insole in Different Body Mass Index Level Females

Background: The higher body mass index is a risk factor that associated with onset and progression of knee osteoarthritis by increasing the knee adduction moment. Lateral wedge insoles are used for reducing the knee adduction moment which may prevent the occurrence of knee osteoarthritis in healthy population.Purpose: The purpose of this study was to assess the effectiveness of the lateral wedge insole among normal, overweight, obese I and obese II female while walking.Methods: A cross-sectional experimental design study was used to investigate 80 females who aged between 18 – 40 years using 3-D Motion Analysis. The peak external knee adduction moment was collected in walking shoes and walking shoes with 5-degree lateral wedge insoles conditions. The significant difference was determined using Paired-T test (p = 0.05).Results: The peak external knee adduction moment was significantly decreased by the effect of shoes with lateral wedge insoles in normal, overweight and obese I (22.12%, 18.34% and 24.15%). However, it did not change in the obese II.Conclusion: The peak external knee adduction moment was decreased by the immediate effect of lateral wedge insoles. It may prevent the onset of knee osteoarthritis in normal, overweight, and obese I. Further study should investigate long term effect of lateral wedge insoles on the knee joint load and the effect of dose in higher body mass index.