Biomechanical Changes in the Lower Limb After a Quadriceps Fatigue Task in Association With Dynamic Knee Valgus

Area of Science:

• Biomechanics
• Sports Medicine
• Orthopedics

Background:

• Dynamic knee valgus (DKV) is linked to anterior cruciate ligament (ACL) injuries.
• The predictive accuracy of DKV for ACL injury requires further investigation.

Purpose of the Study:

• To investigate the effects of fatigue on lower limb biomechanics during jump landing.
• To determine if DKV can be induced by fatigue and identify its biomechanical predictors.

Main Methods:

• Controlled laboratory study involving healthy men performing jump landings after a fatigue protocol.
• Participants were classified into induced and non-induced DKV groups based on knee abduction moment changes.
• Lower limb biomechanics and quadriceps electromyography (EMG) were analyzed.

Main Results:

• The induced DKV group showed reduced hip flexion, lower vertical ground reaction force, and decreased quadriceps EMG amplitude.
• The induced DKV group also exhibited increased hip internal rotation moment.
• Hip internal rotation moment (AUC=0.994) demonstrated the highest discriminative power for DKV occurrence.

Conclusions:

• Fatigue-induced DKV is associated with altered quadriceps activity and hip rotation mechanics.
• These findings offer insights for developing targeted ACL injury prevention strategies.