Using Nonlinear Vibroartrographic Parameters for Age-Related Changes Assessment in Knee Arthrokinematics

Changes in articular surfaces can be associated with the aging process and as such may lead to quantitative and qualitative impairment of joint motion. This study is aiming to evaluate the age-related quality of the knee joint arthrokinematic motion using nonlinear parameters of the vibroarthrographic (VAG) signal. To analyse the age-related quality of the patellofemoral joint (PFJ), motion vibroarthrography was used. The data that were subject to analysis represent 220 participants divided into five age groups. The VAG signals were acquired during flexion/extension knee motion and described with the following nonlinear parameters: recurrence rate ([Formula: see text]) and multi-scale entropy ([Formula: see text]). [Formula: see text] and [Formula: see text] decrease almost in a linear way with age (main effects of group [Formula: see text]; means ([Formula: see text]): [Formula: see text]; and [Formula: see text]. The [Formula: see text] post-hoc analysis showed that there were statistically significant differences ([Formula: see text]) in all comparisons with the exception of the 5th–6th life decade. For [Formula: see text] , statistically significant differences ([Formula: see text]) occurred for: 3rd–7th, 4th–7th, 5th–7th and 6th life decades. Our results imply that degenerative age-related changes are associated with lower repeatability, greater heterogeneity in state space dynamics, and greater regularity in the time domain of VAG signal. In comparison with linear VAG measures, our results provide additional information about the nature of changes of the vibration dynamics of PFJ motion with age.