The influence of ankle joint movement on knee joint kinesthesia at various movement velocities.

The purpose of this study was to determine if gastrocnemius elongation or shortening and direction and velocity of knee movement influenced knee kinesthesia. Healthy volunteers sat with their knee flexed (20 degrees) and was then passively rotated (flexion or extension) at three velocities (0.5, 2, or 10 degrees/s) while the ankle was either fixed or rotated (dorsiflexed or plantar flexed at 0.17, 0.65, or 3.3 degrees/s) creating gastrocnemius elongation or shortening. Subjects activated a thumb switch, stopping motion once they detected onset and direction of the motion. Detection of passive movement sense (DPMS) was the angular movement before activation of a thumb-switch. Significant differences (P=0.003) in the rate of change in DPMS across a variety of movement velocities was observed but shortening or elongation of the gastrocnemius did not affect DPMS. Gastrocnemius elongation/shortening did not affect knee DPMS, simple reaction time plays an important role in testing kinesthesia especially at faster movements. While feedback from the gastrocnemius muscle plays a limited role in healthy subjects, differences in testing velocities may incorporate higher levels of central nervous system processing. Clinical measures of kinesthesia can be affected by both movement direction and movement velocity that are speed dependent.