Quadriceps Muscle Size, Quality, and Strength and Self-Reported Function in Individuals With Anterior Cruciate Ligament Reconstruction

Context: Ultrasound imaging provides a cost-effective method of measuring quadriceps morphology, which may be related to self-reported function after anterior cruciate ligament reconstruction (ACLR). Objective: To compare quadriceps morphology and strength between limbs in individuals with ACLR and matched control limbs and determine their associations with self-reported function. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: Forty-two individuals with ACLR (females = 66%; age = 21.8 +/- 2.6 years; time since ACLR = 50.5 +/- 29.4 months) and 37 controls (females = 73%; age = 21.7 +/- 1.2 years). Main Outcome Measure(s): Quadriceps peak torque (PT) and rate of torque development were assessed bilaterally. Ultrasonography was used to measure the cross-sectional area (CSA) and echo intensity (EI) of the rectus femoris, vastus lateralis (VL), and vastus medialis. Self-reported function was assessed via the International Knee Documentation Committee (IKDC) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales. Paired-samples t tests were calculated to compare involved and uninvolved limbs. Independent t tests were conducted to compare groups (alpha = .05). Linear regression was performed to analyze associations between quadriceps function and self-reported function after accounting for time since ACLR, activity level, and sex, and models for EI added subcutaneous fat as a covariate. Results: Isometric PT did not differ between limbs or groups. Involved limbs had a lower rate of torque development compared with the control (P= .01) but not the uninvolved limbs (P= .08). Vastus lateralis CSA was smaller in the involved than in the uninvolved (P < .01) but not the control limbs (P= .10). Larger VL CSA (Delta R-2 = 0.103) and lower VL EI (Delta R-2 = 0.076) were associated with a higher IKDC score (P < .05). Larger VL CSA was associated with greater KOOS Symptoms (Delta R-2 =0.09, P = .043) and Sport and Recreation (Delta R-2 = 0.125, P = .014) scores. Lower VL EI was associated with higher KOOS Symptoms (Delta R-2 = 0.104, P = .03) and Quality of Life (Delta R-2= 0.113, P = .01) scores. Quadriceps PT and rate of torque development were not associated with IKDC or KOOS subscale scores. Conclusions: Quadriceps morphology was associated with self-reported function in individuals with ACLR and may provide unique assessments of quadriceps function.