Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Neuromuscular Responses to Perturbations during Walking in Knee Osteoarthritis: Influence of Instability, Strength, Proprioception and Stiffness.

Kumar,  Deepak, Reisman,  Darcy, B. Swanik,  Charles, S. Rudolph,  Katherine

Background:

Neuromuscular interventions that reduce disability and slow disease progression are needed for people with knee osteoarthritis (OA). Effective interventions would depend on the ability of the neuromuscular system to adapt to changing external demands, in spite of the deficits in afferent and efferent pathways seen in people with knee OA. The ability of the neuromuscular system to adapt has been studied through the response to repeated perturbations; however, no studies report mechanisms that may accompany successful neuromuscular adaptation in people with knee OA. The aims of this study are to (1) analyze the responses to repeated perturbations during walking in people with knee OA compared to controls, and (2) to analyze the effect of quadriceps strength, functional knee instability (FKI), proprioceptive loss and altered knee stiffness on the responses to repeated perturbations.

Methods:

43 subjects with medial knee OA and 21 healthy controls (C) participated. Kinematic and EMG data were collected as subjects walked overground (Level) for 10 trials and over a platform that translated laterally (Perturbed) at initial contact (IC), for 30 trials. FKI was assessed from the response to the instability question in Knee Outcome Survey. Isometric quadriceps strength was measured at 90° flexion. Proprioception was assessed using Threshold to Detect Passive Motion and Joint Repositioning Sense techniques at 15° flexion. Knee stiffness (toque/degree motion) was assessed by a rapid knee flexion from 30°-50° while seated. Walking data were analyzed over- Preactivation (Pre:100 msec before IC), Loading Response (LR: IC to peak knee flexion) and Midstance (MSt: end of LR to peak knee extension) phases. Mixed ANOVAs and Pearson's correlations were used for statistical analyses.

Results:

OA had lower quadriceps strength than C. There were no differences in proprioception or stiffness. OA had less motion and higher activation than C across all conditions. All groups showed an increase in activation and decrease in motion in the 1st perturbation trial compared to normal walking. No adaptation was seen during preactivation and LR phases but during MSt, there was increased knee motion and deceasedmuscle activation over the 1st 5 trials. Quadriceps strength, knee stiffness, proprioception and FKI were not related to the rate of adaptation.

Discussion:

This is the 1st report of neuromuscular adaptation in people with knee OA, and also for knee stiffness in this population. We found that people with knee OA respond similarly to controls when exposed to repeated lateral perturbations during walking, with an increase in knee motion and decrease in muscle activations. The knee OA related impairments in quadriceps strength, proprioception, stiffness and dynamic stability are not related to the ability to adapt. The results provide evidence that rehabilitation strategies aimed at modifying movement and muscle activation strategies to improve knee stability and reduce joint contact forces may be effective for people with knee OA. Further study is needed to determine the goals and best methods for improving neuromuscular control in this population.

To cite this abstract, please use the following information:
Kumar, Deepak, Reisman, Darcy, B. Swanik, Charles, S. Rudolph, Katherine; Neuromuscular Responses to Perturbations during Walking in Knee Osteoarthritis: Influence of Instability, Strength, Proprioception and Stiffness. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :194
DOI: 10.1002/art.27963

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