Abstract
Purpose
To investigate the relationship between the biomechanical characteristics of lower extremity and anterior cruciate ligament (ACL) loading during single-leg landing in patients with chronic ankle instability (CAI) who have different ankle sprain frequencies within a year.
Study Design:
Cross-sectional study; Level of evidence, 3.
Methods
Ankle sprain occurrences among 74 participants were meticulously documented over one year. The participants were systematically classified into groups based on the monitoring data regarding the frequency of ankle sprains over the course of this year, ranging from 2 to 6 or more incidents. Kinematic, kinetic, and electromyographic data were collected while participants performed a single-leg landing task. Lower extremity muscle force and ACL loading were modeled using OpenSim software.
Results
CAI patients with more than four ankle sprains had higher peak ACL loading during single-leg landing than those with only two or three ankle sprains (P < 0.05). Additionally, CAI patients with more than four ankle sprains exhibited a limited range of ankle dorsiflexion and biceps femoris muscle strength, which was significantly correlated with ACL loading (P < 0.05). CAI patients with more than 5 ankle sprains had greater ankle inversion angle, inversion angular velocity, vertical ground reaction force (GRF), rectus femoris muscle strength, and lower gastrocnemius, soleus muscle force during single-leg landing, and these biomechanical indices were significantly correlated with ACL strain (P < 0.05).
Conclusion
Based on these findings, it appears that experiencing four ankle sprains within a year might be a threshold for the development of knee compensation in CAI patients. This compensation could result in a significant increase in ACL loading. The study also found that CAI patients with more than four ankle sprains commonly exhibited altered motor characteristics such as limited ankle dorsiflexion angle, increased ankle inversion angle, excessive vertical GRF, and insufficient gastrocnemius and soleus muscle force during the landing phase. These characteristics might be responsible for the observed increase in ACL loading.