The Relationship Between the Effects of Lateral Wedge Insoles and Kinematic Chain Dynamics Between the Hindfoot and Lower Leg in Patients With Osteoarthritis of the Knee.

Purpose We aim to determine whether kinematic chain dynamics of the hindfoot and lower leg are involved in the effect of a lateral wedge insole (LWI) on reducing lateral thrust among patients with medial compartment knee osteoarthritis (KOA). Participants and methods Eight patients with knee osteoarthritis were included in the study. Evaluation of the kinematic chain and gait analysis was performed using an inertial measurement unit (IMU). The dynamics of the kinematic chain were calculated as linear regression coefficients of the external rotation angle of the lower leg relative to the inversion angle of the hindfoot during repeated inversion and eversion of the foot in the standing position (kinematic chain ratio (KCR)). Walk tests were performed under four conditions: barefoot (BF), neutral insole (NI) with an incline of 0 degrees, and LWI with an incline of approximately 5 and 10 degrees (5LWI and 10LWI, respectively). Results The mean (± standard deviation (SD)) KCR was 1.4 ± 0.5. The KCR was significantly correlated with the change in 5LWI lateral thrust acceleration relative to BF (r = 0.74). A significant correlation was also observed between changes in the hindfoot evolution angle and lower leg internal rotation angle with a 10LWI with respect to BF and NI, and changes in lateral thrust acceleration. Conclusion The results of this study suggest that the kinematic chain is involved in the effects of an LWI in patients with knee osteoarthritis.

Changes in kinematic chain dynamics between calcaneal pronation/supination and shank rotation during load bearing associated with ankle position during plantar and dorsiflexion.

[Purpose] This study aimed to elucidate the dynamics of the kinematic chain of shank rotation accompanying calcaneal pronation/supination during weight-bearing changes associated with ankle positions during plantar/dorsiflexion and whether this biomechanical phenomenon is affected by age. [Participants and Methods] The study included 54 participants (108 legs, 25 young and 29 old participants). A 3-dimensional motion analysis system measured the calcaneal pronation/supination and the shank rotation angles during pronation/supination of the foot when upright. The kinematic chain ratio was defined as the linear regression coefficient (shank rotation angle/calcaneal pronation/supination angle). The kinematic chain ratio was measured during plantar flexion, in an intermediate position, and dorsiflexion. [Results] Significant differences in the kinematic chain ratio were related to ankle position but not age. The mean kinematic chain ratio in all participants was 0.9 ± 0.3 for plantar flexion, 1.0 ± 0.2 for an intermediate position, and 1.3 ± 0.4 for dorsiflexion, showing significant differences between the 3 ankle positions. [Conclusion] During dorsiflexion, the long axis of the shank and that of the subtalar joint are nearly parallel; thus, shank rotation increases (larger kinematic chain ratio). During plantar flexion, a larger angle is created; thus, shank rotation decreases (smaller kinematic chain ratio). When analyzing the kinematic chain between calcaneal pronation/supination and shank rotation, it is essential to consider the ankle position during plantar/dorsiflexion.

Factors that determine kinematic coupling behavior of calcaneal pronation/supination and shank rotation during weight bearing: ananalysis based on foot bone alignment using radiographic images.

[Purpose] This study aimed to identify factors that determine the kinematic coupling behavior of calcaneal pronation/supination and shank rotation in a standing position. [Participants and Methods] Study participants included 15 healthy adults (30 legs). Kinematic coupling behavior was quantified as the linear regression coefficient (kinetic chain ratio [KCR]) of the angle of shank rotation against the angle of calcaneal pronation-to-supination measured using a 3-dimensional motion analysis system during pronation and supination of both feet while standing. The relationship between the KCR and the foot bone alignment was also analyzed using 35 parameters that were evaluated based on plain radiography. [Results] Greater the height of the medial longitudinal arch, and greater the backward tilt of the long axis of the talus and the backward tilt of the talar articular surface of the calcaneus, larger the KCR. This alignment differed between the genders. [Conclusion] This study suggested that the KCR increases as the subtalar joint axis approaches the long axis of the shank secondary to the lifting of the medial longitudinal arch of the foot and decreases as the subtalar joint axis approaches the long axis of the foot secondary to the lowering of the medial longitudinal arch of the foot.