Forty-nine patients who underwent anterior cruciate ligament (ACL) reconstruction were randomized to early open kinetic chain exercises (EOKC) at 4 weeks or to late OKC (LOKC) exercises at 12 weeks, to compare differences in these rehabilitation methods. After 17 months of comparing both quadriceps strengthening protocols, EOKC with restricted ROM did not differ from a LOKC, in terms of anterior knee laxity. It did, however, have slightly faster recovery in quadriceps strength, which was not clinically significant. There was no difference in pain improvements (assessed using the numeric pain rating scale), functional improvements (measured by Lysholm knee scoring scale) or in single-legged and cross over hop test scores between the two groups.