Summary
The present study revealed that the subjects with asymmetrical knee flexion during landing at 9 months after ACL reconstruction presented greater pain compared to those with symmetrical knee flexion.
Abstract
Background
Asymmetrical knee kinematics during sports activities after ACL reconstruction is one of risk factors in secondary ACL injury. However, it remains unknown what factor causes asymmetrical knee kinematics during sports activities in the patients at an early period after ACL reconstruction.
Purpose
To compare muscle strengths and self-reported outcomes of the subjects with asymmetrical knee flexion during drop vertical jump (DVJ) task at 9 months after ACL reconstruction to those with symmetrical knee flexion.
Methods
This study investigated the knee flexion during DVJ task and knee muscular isokentic strength using Biodex System at 9 months after ACLR with hamstring autograft in 45 male and 80 female athletes (21.5±9.7 years old). Knee flexion from the initial contact to peak knee flexion was assessed during landing from a height of 30 cm using 2D pose estimation AI program “Open Pose” (Zhe C, et al. 2017). The subjects were divided to asymmetrical knee-flexion and symmetrical knee-flexion groups based on minimal detectable change (MDC95) of side-to-side difference in knee flexion during landing. We then compared muscle strengths and self-reported outcomes (IKDC-SKF and KOOS) between the subjects in asymmetrical and symmetrical groups.
Results
Our analysis of repeatability for 2D pose estimation AI program showed that MDC95 of side-to-side difference in knee flexion angle during landing was 6.66 degrees. According to this cut-off value, 35 and 67 subjects were classified to asymmetrical and symmetrical knee-flexion groups, respectively. In the asymmetrical knee-flexion group, KOOS pain score at 9 months after ACL reconstruction, 91.0±9.4, was significantly lower than that of the symmetrical knee-flexion group, 94.9±5.8 (p=0.031). There was no significant difference in quadriceps strength, hamstrings strength, IKDC-SKF, KOOS-symptom, -function, -sports or -QOL.
Conclusions
The present study revealed that the subjects with asymmetrical knee flexion during landing at 9 months after ACL reconstruction presented greater pain compared to those with symmetrical knee flexion. There is, therefore, a possibility that pain management might reduce asymmetrical knee flexion during landing at a relatively early period after ACL reconstruction.
*The authors of the present paper are Nonoka Matsunisi, Tomoya Ishida, Mina Samukawa, Makoto Suzuki, Hisashi Matsumoto, Yu Ito, Miku Sakashita, Yoshimitsu Aoki and Harukazu Tohyama.