The effects of different gait patterns on knee joint biomechanics and dynamic stability during stair ascent in...

This study aimed to investigate the effects of different stair-ascent gait patterns on knee joint biomechanics and dynamic postural stability.

This cross-sectional, repeated-measures laboratory study was approved by the Ethics Committee of Qinhuangdao First Hospital [approval no. (2025K-135-01)]. Experimental procedures were conducted at Qinhuangdao First Hospital, and data analysis was performed at Yanshan University, which served as the collaborating institution for study design and statistical processing. Participants were recruited between 03 December 2024 and 18 December 2024. Fourteen healthy young males (mean age: 19.8 years; mean body mass: 72.2 kg) were enrolled and instructed to ascend stairs using two distinct gait patterns: a regular step-by-step (alternating) pattern, in which one step height was ascended per gait cycle, and a double-step (skip-step) pattern, in which two step heights were ascended per cycle by skipping one intervening step. Kinematic and kinetic data were synchronously recorded using a Qualisys infrared motion-capture system and a Kistler force platform. As each participant performed both conditions, all statistical comparisons were conducted using paired-sample *t*-tests. Dynamic stability and knee loading were quantified by the margin of stability (MOS) and patellofemoral joint stress (PFJS), respectively.

Throughout the gait cycle, no significant difference was observed MOSml between the two gait patterns (P = 0.318). In the anterior-posterior (AP) direction, however, the MOS for both patterns remained negative and decreased over time, with the double-step pattern yielding significantly lower MOSap values compared with the regular step-by-step pattern (P = 0.002). At the instant of left foot-off, significant differences were detected between patterns in right knee joint angle, right knee joint moment, net joint moment, effective quadriceps muscle lever arm, quadriceps force (QF), angle between the quadriceps tendon and patellar ligament, patellofemoral joint force (PFJF), PFJS, and patellofemoral contact area (all P < 0.001).

In healthy young males, the double-step stair-ascent pattern was associated with reduced anterior-posterior dynamic stability, reflecting a decreased anterior-posterior stability margin. This pattern was also associated with elevated PFJS, reflecting greater compressive loading of the knee joint. Because of the cross-sectional design, these findings represent observed associations rather than causal mechanisms. Accordingly, lower-limb strengthening exercises and modifications to stair-climbing strategy may constitute reasonable hypotheses for mitigating stability decline and mechanical loading; however, these should be tested in future studies before being translated into clinical recommendations.