Ultrasound Echo Intensity of the Rectus Femoris Correlates Muscle Strength in the Post-Operative Rehabilitation of Anterior Cruciate Ligament Reconstruction

Introduction: To assess the correlation between corrected rectus femoris echo intensity (C-RF-EI), rectus femoris cross-sectional area (RF-CSA), and quadriceps strength during a 6-month period after anterior cruciate ligament reconstruction (ACL-R). Methods: A retrospective subanalysis of data collected in a randomized controlled clinical trial (IRB 19-008473. NCT ID NCT04302558). Twenty-eight patients aged 13 to 50 years undergoing ACL-R were assessed for C-RF-EI, RF-CSA, and quadriceps strength. Results: The correlation (R) between C-RF-EI and RF-CSA after ACL-R ranged from −0.25 (24 weeks after ACL-R) to −0.34 (4 weeks after ACL-R), which is indicative of a negative linear association. The overall repeated measures correlation was −0.31 (P