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Neuromuscular strategies during gait in women with early and established knee osteoarthritis
Abstract   Peer reviewed

Neuromuscular strategies during gait in women with early and established knee osteoarthritis

A. Mahmoudian, I.A. Baert, I. Jonkers, J.H. van Dieën, F.P. Luyten and S.M. Verschueren
Osteoarthritis and Cartilage, Vol.22
Paris, France, 04/2014
04/2014

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Abstract

Purpose: Osteoarthritis (OA) has become one of the leading causes of pain and disability in the elderly worldwide. Medial compartment knee joint loading during gait, measured indirectly by calculating the external knee adduction moment (KAM), has received the most attention due to its crucial role in knee OA pathogenesis. In a recent study of our group, we showed in this respect that women with "early" knee OA as defined by Luyten et al., did not demonstrate an altered loading pattern yet, whereas women with established OA did show an increased KAM during gait. The neuromuscular adaptations during gait in patients with knee OA have received less attention especially in patients with early OA. The aim of the present study is to assess the differences in gait related neuromuscular activity in subjects with early OA compared to healthy controls and established OA patients. Methods: Eighty-five women enrolled in the present study. Knee OA patients were sub-classified into early (n = 27) and established (n = 29) medial knee OA groups based on the recent classification system for early OA, which combines magnetic resonance imaging with radiographic and clinical findings. Twenty-nine age-matched asymptomatic subjects formed the control group. Knee symptoms and function were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) (Dutch version). 3Dgait analysis was performed whereby bilateral muscle activity of rectus femoris (RF), Medial Hamstrings (MH), vastus lateralis (VL), vastus medialis (VM), gluteus medius (GM), and gastrocnemius (GC) was recorded with surface electromyography (EMG). The EMG was normalized to the peak muscle activity of each muscle found within each walking trial. Afterwards the mean and maximum EMG activities were calculated. Co-contraction indices (CCI) were calculated for 3 pairs of muscles (VM-MH, VM-MGC, and VL-MH) using the method of Rudolph et al. (2000). Results: Subjects with established OA had significantly lower knee symptoms and function scores on KOOS compared to healthy controls or patients with early OA. There were no significant differences between the three groups in the mean normalized muscle activity during the stance phase of gait. Comparing mean activity of the two vasti muscles during the stance phase of gait within each group, however, revealed that the patients with established OA had a significantly higher activity of vastus lateralis compared to vastus medialis (p ˂ 0.05) in the involved leg but not in the contralateral leg. There was no difference between the 3 groups in duration of muscle activation as percentage of the stance phase of the gait cycle. The CCI for the Medial Gastrocnemius-Vastus Medialis was decreased in the early OA group compared to the healthy controls and the established OA group, although this difference did not reach significance (p = 0.09). Conclusions: Patients with early OA did not show similar alterations in neuromuscular control compared to the established OA patients. The tendency of patients with early OA to decrease medial co-contraction might be a strategy to reduce medial compartment knee joint loading. Comparable to previous studies, patients with established OA showed some neuromuscular adaptations, such as an increased activation of vastus lateralis compared to vastus medialis. Other previously reported findings, like an increased duration of muscle activation, were not replicated in this study. Neuromuscular adaptations during gait appear to occur later in the disease process, thus they probably aren’t risk factor in knee OA pathogenesis.

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