Functional assessments of the knee joint biomechanics by using pendulum test in adults with Down syndrome

Abstract

In this study, we assessed kinematics and viscoelastic features of knee joint in adults with Down syndrome (DS) by means of the Wartenberg pendulum test. This test allows the measuring of the kinematics of the knee joint during passive pendular motion of leg under the influence of gravity. In addition, by a combination of kinematic and anthropometric data, pendulum test provides estimates of joint viscoelastic properties by computing damping and stiffness coefficients. To monitor the occurrences of muscle activation, the surface electromyogram (EMG) of muscle rectus femoris was recorded. The experimental protocol was performed in a group of 10 adults with DS compared with 10 control adults without DS. Joint motion amplitude, velocity, and acceleration of the leg during the first knee flexion significantly decreased in persons with DS with respect to those without DS. This behavior was associated with the activation of rectus femoris in subjects with DS that resulted in increasing of joint resistance shortly after the onset of the first leg flexion. The EMG bursts mostly occurred between 50 and 150 ms from the leg flexion onset. During the remaining cycles of pendular motion, persons with DS exhibited passive leg oscillations with low tonic EMG activity and reduced damping coefficient compared with control subjects. These results suggest that adults with DS might perform preprogrammed contractions to increase joint resistance and compensate for inherent joint instability occurring for quick and unpredictable perturbations. The reduction of damping coefficients observed during passive oscillations could be a predictor of muscle hypotonia.

Early compensatory and anticipatory postural adjustments following anterior cruciate ligament reconstruction

“…During the unpredictable condition of the present study, almost all the latencies of the compensatory responses recorded in the knee extensor and flexor muscles of healthy participants fell below either 50 or 100 ms (VL: 94,2 %; RF: 95,5 %; BF: 77,3 %) and may then be considered short-and long-latency reflexes (Matthews 1991;Casabona et al 2012). Conversely, almost all the latencies of the knee extensor and flexor muscles recorded in patients with ACLR fell above either 50 or 100 ms (VL: 90,9 %; RF: 90,9 %; BF: 93,9 %) and may then be considered long-latency 13 reflexes or voluntary responses (Pruszynski and Scott 2012;Valle et al 2013).…”

“…Since long-loop circuits are involved, this process can take place, thus allowing the sensory signal to be specifically associated to the task and the motor response to be adapted instantaneously to the actual circumstances (Lewis et al 2006;Kurtzer et al 2008;Pruszynski and Scott 2012;Pruszynski et al 2011;Casabona et al 2012;Valle et al 2013).…”

Relationships between Muscle Architecture of Rectus Femoris and Functional Parameters of Knee Motion in Adults with Down Syndrome

“…This means that the pennation angle may be considered the morphological correlation of the phasic activation of the RF after the leg release. In previous papers we showed that this muscle activity appears when persons with DS pass from adolescence to the adult age, indicating a possible functional compensation for the inherent ligaments laxity [13, 14]. Thus, changes in pennation angle may be a structural sign associated with specific functional adaptations occurring in DS when rapid muscle activations are required.…”

“…The analysis of the knee motion was performed using the pendulum test (for an extensive description of this procedure see Casabona et al, [13]). By means of this technique, angle amplitude variations at the knee were recorded by an electrogoniometer placed on the lateral side of the tested limb.…”

“…For example, from adolescence to adult age, persons with DS develop adaptive neuromuscular responses to muscle hypotonia and ligament laxity following the sudden release of leg [14]. In fact, adults with DS showed an increase in reflex muscle activity with respect to adults without DS during the leg dropping [13]. …”