Decreased Thigh Muscle Cross-Sectional Area Following Anterior Cruciate Ligament Injury Depends on Concomitant Meniscal Injury and Subject Sex.

This study characterized acute changes in thigh muscle cross-sectional area (CSA) in subjects who suffered their first severe knee trauma. Ninety-one males and females who suffered ACL rupture with or without concomitant meniscus injury underwent bilateral mid-thigh axial T1-weighted, fast field echo magnetic resonance imaging early after the index trauma and prior to reconstruction. The extensor and flexor muscle groups were segmented bilaterally, and CSA measured. Within-person injured-to-contralateral normal side differences in CSA (injured minus normal limb) were evaluated. ACL-injured male and female subjects were classified into four meniscal injury groups (lateral, medial, both lateral and medial, or normal meniscus). A separate sample of healthy subjects with no history of knee injury or disease underwent the same protocol to determine the magnitude of side-to-side differences in thigh muscle CSA in uninjured individuals. ACL-injured individuals had a substantially greater between-leg differences in thigh extensor muscle CSA after injury and prior to reconstruction than healthy subjects. The between leg difference in thigh extensor muscle CSA of the injured leg was largest in males with meniscus injury involving both compartments, with males having twice as much atrophy of the extensor muscles in the injured leg compared to females in that group. The sex-specific response of thigh muscle to severe knee trauma involving the ACL and meniscus suggests that males and females may require tailored rehabilitation programs pre- and post-surgery to recover muscle size and improve muscular strength and symmetry.