[show abstract][hide abstract] ABSTRACT: The purpose of this study was to identify differences in knee proprioceptive accuracy between subjects with early knee osteoarthritis (OA), established knee OA, and healthy controls. Furthermore, the relation between proprioceptive accuracy on the one hand and functional ability, postural balance, and muscle strength on the other hand was also explored. New MRI-based classification criteria showing evidence of beginning joint degeneration have been used to identify subjects with early knee OA. A total of 45 women with knee OA (early OA, n = 21; established OA, n = 24) and 20 healthy female control subjects participated in the study. Proprioceptive accuracy was evaluated using the repositioning error of a knee joint position sense test using a three-dimensional motion analysis system. Subjective and objective functional ability was assessed by the knee injury and osteoarthritis outcome score, the timed "Up & Go" test, and the stair climbing test. The sensory organization test measured postural control. Muscle strength was measured by isokinetic dynamometry. Early OA subjects showed no significant differences in proprioceptive accuracy compared to healthy controls. In contrast, established OA subjects showed a higher repositioning error compared to early OA subjects (+29 %, P = 0.033) and healthy controls (+25 %, P = 0.068). Proprioceptive accuracy was not significantly associated with functional ability, postural balance, and muscle strength. Knee joint proprioceptive deficits were observed in established OA but not in early OA, suggesting that impaired proprioception is most likely a consequence of structural degeneration, rather than a risk factor in the pathogenesis of knee OA. Impaired proprioceptive accuracy was not associated with disease-related functionality in knee OA patients. Treatment strategies designed to address proprioceptive deficits may be not effective in prevention of knee OA progression and may have no impact on patients' functionality. However, this should be confirmed further in well-designed clinical trials.
[show abstract][hide abstract] ABSTRACT: We previously observed that transient vascular occlusion in volunteers increased the estimation of force exertion with no change in peripheral nerves or muscles. We hypothesized that the primary factor responsible for the overestimation of force exertion during occlusion was the centrally generated motor command, as hypothesized by McCloskey (1974, 1978, 1981). In the present study, we tested the hypothesis that transient vascular occlusion increases the excitability of the primary motor cortex (M1) during force exertion. Healthy human volunteers lay on a bed and squeezed a dynamometer in their right hand. Repetitive gripping forces were exerted at 20%, 40%, or 60% of maximum force, with or without transient (20 s) vascular occlusion of the proximal portion of the right upper arm. During the task, single-pulse transcranial magnetic stimulation was applied to the contralateral M1 to induce motor evoked potentials (MEPs) in the flexor carpi ulnaris (FCU) muscle. The MEP amplitudes were enhanced with occlusion under all conditions, with the exception of 60% contraction. In contrast, no significant difference was observed between the MEP amplitudes obtained from the occluded or non-occluded, relaxed FCU muscle. These results suggest that transient vascular occlusion increases the excitability of M1 only during force exertion.
Neuroscience Research 06/2013; · 2.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Information from cutaneous, muscle and joint receptors is combined with efferent information to create a reliable percept of the configuration of our body (proprioception). We exposed the hand to several horizontal force fields to examine whether external forces influence this percept. In an end-point task subjects reached visually presented positions with their unseen hand. In a vector reproduction task, subjects had to judge a distance and direction visually and reproduce the corresponding vector by moving the unseen hand. We found systematic individual errors in the reproduction of the end-points and vectors, but these errors did not vary systematically with the force fields. This suggests that human proprioception accounts for external forces applied to the hand when sensing the position of the hand in the horizontal plane.
PLoS ONE 01/2013; 8(9):e74236. · 3.73 Impact Factor
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