2023, Vol. 27 ›› Issue (4): 520-526

Three-dimensional motion analysis of lower limb biomechanical performance in Tai Chi practitioners accompanied by knee joint pain

Li Yaping1, 2, Liu Hong1, 2, Gao Zhen1, 3, Chen Xiaolin1, 2, Huang Wujie4, Jiang Zheng1, 2   

Abstract: BACKGROUND: Tai Chi practice can cause knee pain symptoms in many individuals. There is currently less research on the characteristics of practitioners with knee pain from a biomechanical view.
OBJECTIVE: To explore the differences in biomechanical characteristics of the lower limbs in Tai Chi practice by three-dimensional motion system between practitioners who experience knee pain and healthy practitioners.
METHODS: Six practitioners with knee pain were selected into an experimental group, while six healthy practitioners were chosen into a control group. Three-dimensional motion capture system was used to record the kinematics and dynamics of the lower limbs during Brush Knee and Twist Step in both groups. The motion characteristics at the characteristic moment of ground reaction force were compared. The characteristic moment of ground reaction force included the front support leg ground reaction force peak time in the left/right Brush Knee and Twist Step propulsion period (T1/T5), the left leg ground reaction force trough time in the right Brush Knee and Twist Step recoil turning period (T2), the ground reaction force first peak time in the right Brush Knee and Twist Step single support period (T3), the ground reaction force second peak time in the right Brush Knee and Twist Step single support period (T4).  
RESULTS AND CONCLUSION: (1) Kinematic parameters: The difference in step length, step width and centroid height was not statistically significant between the two groups (P > 0.05). Compared with the control group, the experimental group had a greater hip abduction angle of the posterior support leg (P < 0.05) at T1 and T5; the left knee adducted at T2 and T3, and the right knee adducted at T5 (P < 0.05); a smaller abduction angle in right knee at T2 and T4 (P < 0.05). (2) Kinetic parameters: Compared with the control group, the experimental group had lower vertical ground reaction force (P < 0.05) at T3, T4 and T5; a smaller hip extension moment of the front support leg (P < 0.05) at T1 and T5; a lower hip rotation moment of the front support leg (P < 0.05) at T5. The total support moment contribution of knee joint in the experimental group was greater (P < 0.01) at T1. (3) The results suggested that compared with the healthy trainers, the practitioners with knee pain symptom reduced their force on the ground. The differences in kinematic and kinetic parameters between the two groups were concentrated in the hip and knee joints. They showed less hip extension and rotation, larger knee adduction, and larger the total support moment contribution of the knee joint. Therefore, when retraining Tai Chi for trainers with knee pain, it is necessary to consider the adjustment from the movement patterns of the practitioner’s hip and knee joints.
Key words: Tai Chi, Brush Knee and Twist Step, knee pain, joint angle, joint moment, biomechanics