Vastii muscle adaptation caused by Quadriceps weakness observed after an Anterior Cruciate Ligament reconstruction (ACLr) remain debatable. We described the time course of changes in Quadriceps thickness, strength, and thigh circumference over six months following an ACLr. Quadriceps thicknesses, Quadriceps strength, and thigh circumference were measured preoperative, 3, and 6 months post-ACLr surgery in 103 patients (77 men and 26 women). Limbs and time were compared with repeated-measures ANOVA and the Intra-class correlation coefficient was determined (α = 5 %). From 0 to 3 months post-surgery, Quadriceps strength (p < 0.05), and VI (p < 0.05) and VL (p < 0.001) thicknesses were reduced. From 3 to 6 months, Quadriceps strength (p < 0.05), total Quadriceps thickness (p < 0.001), and VI (p < 0.001) and VL (p < 0.05) thicknesses increased. VM and RF thicknesses increase to 3 months after ACLr (p < 0.05). Quadriceps strength, circumference at 5 cm, VI, VL, VM, and total Quadriceps thickness remain lower than the contralateral limb 6 months following an ACLr (p < 0.05). Quadriceps thickness adapts heterogeneously, with VI and VL atrophying for up to three months, developing the highest Quadriceps weakness. By 6 months, VI does not recover its thickness proportion, and VI and VL do not return to pre-surgery conditions. Both vastii muscles align with Quadriceps strength changes over six months posterior ACLr.