Despite the fact that anterior cruciate ligament reconstruction (ACLR) is a common procedure, no clear guideline regarding the timing of reconstruction has been established. We hypothesized that there is a point in post injury period, after which significant increase in meniscal tears occurs. The purpose of this study was to derive a guideline in order to reduce the rate of secondary meniscal tears in the ACL-deficient knee. A total of 451 patients were retrospectively studied and divided into six groups according to the time from injury to ACLR: (a) 105 patients had undergone ACLR within 1.5 months post injury, (b) 93 patients within 1.5-3 months, (c) 72 patients within fourth to sixth month, (d) 56 patients within seventh to twelfth month, (e) 45 patients within the second year and (f) 80 patients within the third to fifth year. The presence of meniscal tears was noted at the time of ACL reconstruction and then recorded and statistically analysed. Fifty-three (50.5%) patients from group a, 46 (49.5%) from group b, 39 (54.2%) from group c, 31 (68.9%) from group d, 28 (62.2%) from group e and 54 (67.5%) from group f had meniscal tear requiring treatment. The statistical analysis demonstrated that the earliest point of significantly higher incidence of meniscal tears was in patients undergoing ACLR more than 3 months post injury. Therefore, ACLR should be carried out within the first 3 months post injury in order to minimise the risk of secondary meniscal tears.