Kim HJ, Lee JH, Ahn SE, Park MJ, Lee DH. Influence of Anterior Cruciate Ligament Tear on Thigh Muscle Strength and Hamstring-to-Quadriceps Ratio: A Meta-Analysis. PLoS One. 2016;11(1):e0146234. Published 2016 Jan 8. doi:10.1371/journal.pone.0146234

After ACL both hamstring and quadriceps loose strength

However, we often see a decrease in quadriceps strength and therefore hamstring quadsratio can be missleading because it is due to they are really weak in there quadriceps