Perception of leaning backward while standing and patellar movement.

[Purpose] The purpose of this study was to investigate the relationship between the patellar movement and the standing backward leaning perceptibility. [Subjects and Methods] Fourteen volunteers who were confirmed presence of upward patellar movement during backward leaning from the quiet standing posture participated in this study. The quiet standing position, the standing backward leaning position at patellar movement onset and standing position perceptibility were measured. The position of the center of pressure in the anteroposterior direction in standing is represented as the percentage distance from the hindmost point of the heel in relation to the foot length (%FL). [Results] The mean value of the center of pressure on anteroposterior direction positions in quiet standing was 43.2%FL. The patellar movement onset position was 35.1%FL. The individual mean value of standard deviations for the onset position was 2.5%FL. The absolute error at the onset position is specifically and significantly small. [Conclusion] For the subjects whose patellas move during backward leaning in this study, the standing position near the onset position was perceived accurately, probably by the substantial change in sensory information associated with the onset of patellar movement while backward leaning.