Movement of gastrocnemius muscle tendon by ankle joint passive plantar/dorsiflexion exercise. Changes by knee joint flexion angle

Aim. We have reported in our previous studies that the maximal flexion of the knee joint relaxes the origin side of the gastrocnemius muscle and increases the dorsiflexion angle of the ankle joint. This effect in living bodies has not yet been reported, however. In this study, the movement of the gastrocnemius muscle tendon following ankle joint passive plantar/dorsiflexion exercise with different knee joint flexion angles (0, 30, 60, 90, and 120) was studied using an ultrasonic diagnostic imaging system. Methods. The ankle joint was fixed by BIODEX, and the ankle joint passive plantar/dorsiflexion exercise was conducted from plantar flexion of 5 to the maximal dorsiflexion position at 5/sec. The measurement sites were the deep aponeurosis (DA) of the medial head of the gastrocnemius muscle and the musculotendinous junction (MTJ), and at every 1 of plantar/dorsiflexion. Results. The maximal dorsiflexion angle of the ankle joint at the respective knee joint angles increased with an increase in knee joint flexion angle. It was shown for all the knee joint angles that: (1) the DA and the MTJ moved distally with an increase in dorsiflexion angle of the ankle joint and (2) the MTJ tended to exhibit higher values than the DA. Conclusion. The dorsiflexion angle of the ankle joint increased with an increase in flexion angle of the knee joint. It was confirmed that the MTJ moved largely when the knee joint was flexed to relax the origin side of the gastrocnemius muscle and the ankle joint was plantar/dorsiflexed.