title: 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.
authors.affiliation: Gait Analysis Laboratory, Physical Medicine and Rehabilitation Residency Program, University of Catania, Catania, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Casabona
authors.forename: Maria Stella
authors.initials: MS
authors.lastname: Valle
authors.forename: Mariangela
authors.initials: M
authors.lastname: Pisasale
authors.forename: Maria Rosita
authors.initials: MR
authors.lastname: Pantò
authors.forename: Matteo
authors.initials: M
authors.lastname: Cioni
mesh_terms: D000054:Acceleration; D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D053587:Arthrometry, Articular; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004314:Down Syndrome / Q000503:physiopathology*; D004548:Elasticity; D004576:Electromyography; D005260:Female; D006112:Gravitation; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D009119:Muscle Contraction; D009123:Muscle Hypotonia / Q000503:physiopathology; D010808:Physical Examination; D011237:Predictive Value of Tests; D052097:Quadriceps Muscle / Q000503:physiopathology*; D016059:Range of Motion, Articular; D013997:Time Factors; D014783:Viscosity; D055815:Young Adult