Fifty five athletes with anterior cruciate ligament injury scheduled for reconstruction were randomized to low-load strengthening with active blood flow restriction (n=28) or to standard-of-care strengthening with a sham unit (n=27), delivered 1 month pre-op and 4–5 months post-op within the same rehabilitation protocol. The primary outcome was quadriceps muscle strength (isometric and isokinetic peak torque and rate of torque development). Secondary outcomes included knee biomechanics (peak knee flexion angle, peak knee extensor moment), quadriceps morphology (physiological cross-sectional area, T1ρ as a fibrosis proxy), and muscle physiology (fiber type/distribution, fiber cross-sectional area, satellite cells, collagen, and fibrogenic/adipogenic progenitors). Outcomes were assessed at baseline (pre-op) and 4–5 months post-op. Overall, the results revealed no between-group differences for any primary or secondary endpoint. In short, adding blood flow restriction to an otherwise guideline-based program did not improve quadriceps recovery versus sham.