Knee joint rotation center displacement can be estimated in vivo through the analysis of helical axis (HAs) dispersion. HAs can be analyzed during walking, providing information on joint stability. The study aim was to describe knee HAs dispersion during walking in dominant and non-dominant legs of young and elderly healthy subjects.

Twenty young (YG: age 23.3±2.4 years) and twenty elderly (EG: age 69.3±4.6 years) healthy subjects were asked to walk on a treadmill at a self-selected speed with reflective markers placed bilaterally on thighs and shanks to detect HAs dispersion and knee kinematics with an optoelectronic system. HAs dispersion was described during the following four phases of gait cycle: 1) flexion from 95% of the previous gait cycle to 10% of the subsequent gait cycle, 2) extension from 10% to 40%, 3) flexion from 40% to 75% and 4) extension from 75% to 95% of the gait cycle. Mean Distance (MD) and Mean Angle (MA) were used as HAs dispersion indexes during each gait phase.

Participants showed greater MD and MA in sagittal and frontal planes during the first and second phases. EG revealed higher MD (p=0.001) and MA (p<0.001) during the first phase and higher MA (p=0.001) during the fourth phase in both dominant and non-dominant legs on the sagittal plane.

HAs dispersion could be related to the amount of forces acting on knee (first two phases) and knee degeneration (elderly). These results may be used as reference data in further studies on HAs dispersion in presence of knee pathologies or after knee surgery or rehabilitation.

膝关节转动中心位移可以被估计在体内通过螺旋轴（HAS）分散体的分析。可以在行走过程中分析HA，提供关节稳定性的信息。该研究的目的是描述年轻人和老年人健康受试者的优势和非优势腿行走过程中膝关节HAs的散布。

20名健康青年（YG：23.3±2.4岁）和20名老年（EG：69.3±4.6岁）健康受试者被要求以自行选择的速度在跑步机上行走，并在大腿和小腿两侧放置反光标记，以检测HA光电系统的色散和膝运动学。在步态周期的以下四个阶段中描述了HA的分散：1）从先前步态周期的95％弯曲到后续步态周期的10％，2）从10％伸展到40％，3）从40％弯曲到75％和4）从步态周期的75％扩展到95％。在每个步态阶段，将平均距离（MD）和平均角度（MA）用作HA的分散指数。

在第一和第二阶段，参与者在矢状面和额叶面显示出更大的MD和MA。EG在矢状面上的显性和非显性腿中均显示出第一阶段的较高MD（p = 0.001）和MA（p <0.001），第四阶段较高的MA（p = 0.001）。

HAs的散布可能与作用在膝盖上（前两个阶段）和膝盖退化（老人）的力量有关。这些结果可用作进一步研究膝关节病变或膝关节手术或康复后HAs扩散的参考数据。