Using Time-Frequency Analysis to Characterize Altered Knee Dynamics in Post ACL Reconstruction Individuals.

Area of Science:

• Orthopedics
• Biomechanics
• Rehabilitation Science

Background:

• Anterior cruciate ligament (ACL) injuries affect over 250,000 individuals annually in the US, often leading to persistent neuromuscular deficits and knee osteoarthritis despite rehabilitation.
• Traditional biomechanical analyses rely on time-domain metrics, which may not fully capture the complex knee loading dynamics post-ACL reconstruction.

Purpose of the Study:

• To investigate differences in knee loading dynamics between healthy controls and individuals post-ACL reconstruction during running.
• To evaluate the utility of Smoothed Pseudo Wigner-Ville (SPWV) time-frequency analysis in detecting these differences.

Main Methods:

• Smoothed Pseudo Wigner-Ville (SPWV) analysis was employed to examine knee loading patterns in individuals who underwent ACL reconstruction and in healthy controls during running.
• Comparison of time-frequency metrics, specifically the low frequency to high frequency (LF/HF) ratio, between injured, non-injured, and healthy limbs.

Main Results:

• Individuals post-ACL reconstruction demonstrated significantly different loading strategies in their injured limb compared to their non-injured limb.
• The injured limb exhibited a stiffer, more restrictive movement strategy (higher LF/HF ratio), while the non-injured limb showed more oscillatory motion (p<0.001).
• Conventional time-domain metrics failed to detect these inter-limb differences.

Conclusions:

• SPWV analysis effectively identifies distinct knee loading strategies in individuals post-ACL reconstruction that are not discernible through traditional time-domain metrics.
• This time-frequency technique offers a valuable quantitative and visual tool for monitoring joint health and guiding rehabilitation in ACL-injured patients.