Quadriceps function relates to muscle size following ACL reconstruction

Area of Science:

• Orthopaedic Surgery
• Sports Medicine
• Rehabilitation Science

Background:

• Persistent quadriceps weakness and dysfunction are common after anterior cruciate ligament reconstruction (ACLR).
• The specific contribution of reduced quadriceps muscle volume and cross-sectional area (CSA) to these deficits remains unclear.

Purpose of the Study:

• To investigate the relationship between quadriceps muscle cross-sectional area (CSA) and functional outcomes in individuals with persistent weakness post-ACLR.
• To identify which quadriceps muscle CSA factors predict knee and quadriceps function after ACLR.

Main Methods:

• A cohort study involving 30 participants with primary, unilateral ACLR and quadriceps activation failure.
• Assessment of International Knee Documentation Committee (IKDC) score, normalized knee extension MVIC torque, and quadriceps central activation ratio (CAR).
• Magnetic resonance imaging (MRI) to measure quadriceps CSA and volume, including individual muscle estimates in the mid-thigh region.

Main Results:

• Knee extension MVIC torque strongly correlated with Vastus Intermedius (VI) CSA (r=0.857) and quadriceps volume (r=0.830).
• Partial VI volume showed a weak correlation with IKDC score (r=0.365).
• VI CSA alone (R²=0.725) or combined with Vastus Medialis (VM) CSA (R²=0.756) strongly predicted knee extension MVIC torque.

Conclusions:

• Atrophy of the VI and VM muscles is a significant factor negatively impacting knee extension strength following ACLR.
• Targeting VI and VM muscle size may be crucial for improving functional recovery after ACLR.