Quadriceps Muscle Quality Does Not Reflect Self-report Or Muscle Function In Individuals With Acl Reconstruction

Abstract

Chronic quadriceps dysfunction following anterior cruciate ligament reconstruction (ACLR) leads to disability and has been implicated as a risk factor for knee osteoarthritis (OA). However, the most appropriate quadriceps function assessment for identifying individuals at heightened risk of OA and disability is unclear. Quadriceps muscle quality (QMQ) assessed via ultrasound imaging is associated with quadriceps strength and functional ability in the elderly, but has yet to be evaluated following ACLR. PURPOSE: To compare QMQ between limbs and evaluate relationships between QMQ, quadriceps function, and self-report function in individuals with ACLR. METHODS: Twenty-six individuals with unilateral ACLR (73% females; age = 23 ± 3 yr; time since ACLR = 56 ± 45 months; International Knee Documentation Committee Index [IKDC] = 87 ± 9) volunteered for this study. QMQ was calculated as the echo intensity of cross-sectional ultrasound images of the rectus femoris (RF) and vastus lateralis (VL), and averaged as a composite quadriceps value. Isometric (peak torque and rate of torque development) and isokinetic (peak torque and power at 180°/s) quadriceps function was assessed in the ACLR limb and normalized to body mass. QMQ was compared between limbs via paired t-tests, and relationships between QMQ, quadriceps function, and self-report function (IKDC) were evaluated via Pearson correlations. RESULTS: QMQ did not differ between limbs for the RF (arbitrary grayscale units: 110 ± 8 vs. 110 ± 7, p = 0.472), VL (112 ± 9 vs. 113 ± 9, p = 0.203), or quadriceps composite (111 ± 8 vs. 112 ± 7, p = 0.326), and was not correlated with any quadriceps function index (r = -0.283 - 0.122, p > 0.05). IKDC was not correlated with QMQ of the VL (r = -0.093, p = 0.332) or quadriceps composite (r = -0.242, p = 0.127), but poorer RF QMQ was associated with poorer self-report function (r = -0.376, p = 0.035). CONCLUSIONS: Poor QMQ of the RF is indicative of poor self-report function, but QMQ does not differ between limbs and is not associated with quadriceps function in individuals with ACLR. These data suggest that QMQ has limited clinical application for identifying individuals at heightened risk of OA and disability following ACLR. Previous reports of associations between QMQ and muscle function in elderly subjects likely reflect age-related sarcopenia.