Abstract: BACKGROUND: Unilateral knee osteoarthritis patients experience abnormal alterations in lower extremity gait biomechanics, yet few studies have analyzed changes in gait dynamics and muscle activation in knee osteoarthritis patients from the perspective of gait asymmetry. 
OBJECTIVE: To explore the effects of unilateral knee osteoarthritis on gait dynamics and muscle activation asymmetry in elderly women. 
METHODS: Thirty female patients with unilateral knee osteoarthritis attending Beijing Jishuitan Hospital Guizhou Hospital from October 2023 to March 2024 were selected as the knee osteoarthritis group, and 30 healthy elderly females without musculoskeletal disorders from the neighboring community were recruited as the control group. The kinetic and muscle activation levels of the subjects in both groups during walking were synchronously collected by a P-6000 force platform and a Free EMG300 surface EMG device. Kinetic parameters included the first and second peak forces of vertical ground reaction force. Muscle activation indexes included normalized root mean square values of rectus femoris, long head of biceps femoris, and lateral gastrocnemius muscle during the braking and pushing phases. Asymmetry index of the kinetic and muscle activation indexes were calculated separately in patients with K-L grade II and III knee osteoarthritis and controls and compared between groups by independent samples t-test and one-way analysis of variance. 
RESULTS AND CONCLUSION: (1) The difference between the second peak of vertical ground reaction force of both limbs in the knee osteoarthritis group was statistically significant (P < 0.05), as well as the difference between the standardized root mean square of rectus femoris in the braking phase and gastrocnemius and biceps femoris in the pushing phase (P < 0.05). (2) In terms of asymmetry index, the difference between the asymmetry index values of the first peak of vertical ground reaction force between the two groups of subjects was not statistically significant (P > 0.05), while the difference between the second peak asymmetry index values was statistically significant (P < 0.05). The difference in asymmetry index values of standardized root mean square of rectus femoris muscle during the braking phase as well as gastrocnemius and biceps femoris muscles during the pushing phase was statistically significant between the two groups of subjects (P < 0.05). (3) The asymmetry index of the standardized root mean square values of the second peak of vertical ground reaction force, rectus femoris in the braking phase, gastrocnemius in the pushing phase, and biceps femoris in the osteoarthritis group of the knee with K-L classification grade II and III were significantly higher than those of the control group (P < 0.05). The asymmetry indices of standardized root mean square values of the second peak of vertical ground reaction force, rectus femoris in the braking phase and biceps femoris in the pushing phase were higher in the osteoarthritis group of the knee with K-L classification III than in the osteoarthritis group of the knee with classification II (P < 0.05). (4) The asymmetry indices of the second peak of vertical ground reaction, the rectus femoris muscle in the braking phase, and the muscle activation of the biceps femoris and gastrocnemius muscles in the pushing phase can be used as an important index for identifying gait asymmetry in the knee osteoarthritis, which is helpful in providing a theoretical basis for the development of rehabilitation treatment programs. It is also worth noting that extra attention should be paid to patients with higher severity of knee osteoarthritis in the clinical monitoring of gait asymmetry. 

Key words: knee osteoarthritis, dynamics, surface electromyography, asymmetry, gait