Abstract
BackgroundHigh 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.MethodsThis 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.ResultsThe 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.ConclusionsPath 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.
Highlights
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
It is essential to consider the degree of OA severity when exploring the relationship between KAM and pain intensity in view of the fact that such a relationship was very likely to be specific to radiographic severity, Peak external knee flexion moment (KFM) reflected joint loading, and the load would trigger pain in participants with knee OA
The main goal of this study was to investigate the relationships between KAM and pain intensity in people with mild-to-moderate medial knee OA by path analysis taking the effects of KFM, disease severity, joint alignment and walking speed into considerations
Summary
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. It is essential to consider the degree of OA severity when exploring the relationship between KAM and pain intensity in view of the fact that such a relationship was very likely to be specific to radiographic severity, Peak external knee flexion moment (KFM) reflected joint loading, and the load would trigger pain in participants with knee OA. In view that KAM and KFM occur nearly simultaneously with the first peak of medial joint contact force at about the initial 23 % of the total gait cycle [18], Simic et al reported that increase in KFM was associated with a reduction in KAM with gait modification [19] They found that KAM would drop but KFM would rise with toe-in gait; whereas the opposite was observed with toe-out gait during the first half of stance phase in people with knee OA [19]. In order to better understand the relationship between KAM and pain, an analysis on the simultaneous change between KAM and KFM when taking into considerations of factors such as joint alignment [21] and walking speed [22] might better explain the direct relationship between KAM and pain
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