## 4 Discussion
Our data suggest that normalization of the signal make take even longer. The question \"what would be the best time for patients to return to full sport activity\" remains unanswered. We did not find any significant association between graft maturity and age of the patient at the time of surgery. However, further studies including more heterogeneous groups are needed, as our group of patients was rather young (mean age 28 years old). Sex of the patient did not have an effect on graft maturity. On the other hand, full weight bearing immediately after surgery seemed to improve graft remodeling with smaller values of signal intensity. This finding is in accordance with a study performed by [PERSON] et al. [20] showing that appropriate mechanical loading improves healing and remodeling process. [PERSON] et al. [21] demonstrated that postoperative MRI of the ACL graft might accurately predict the risk of re-rupture of the ACL graft. Our study also presents a good correlation between measured SNQ and secondary symptoms of graft insufficiency. A particularly interesting finding of this study is that regardless of initial graft tension at the time of surgery, in order to obtain proper positioning of the tibia relative to the femur, the trend of subsequent anterior tibia subluxation remains comparable. Specifically, patients with over-tension (starting with posterior tibia subluxation) end up with smaller degrees of anterior tibia subluxation at 96 weeks. Currently, pre-operative rehabilitation for chronic patients aimed at reducing anterior tibia subluxation might play a key role for final outcome, facilitating proper positioning of the tibia versus femur intraoperatively. The question regarding the best time to come back to full sports activity remains unanswered, and the literature is conflicting at that point. [PERSON] et al. [22] concluded that the best situation would be patient-tailored rehabilitation protocols and return to sport criteria based on individual characteristics. On the other hand, SIGASCOT (Italian Society of Knee, Arthroscopy, Sport, Cartilage and Orthopaedic Technologies) published with [PERSON] et al. [23] data reflecting on return to sport after ACL reconstruction. 123 SIGASCOT members took part in 14 questions survey focusing, among other things, on return to sport criteria. Returning to non-contact sports was allowed within six months by 87% of members and 53% for contact sports. Return to competitive sport was allowed after six months for 48% for non-contact sports and only 13% for contact sports. The most used criteria to qualify for return to sport were a full range of motion (77%), Lachman test (65%), and Pivot-Shift test (65%). MRI criteria were used only by 12% of surgeons. [PERSON] et al. [24] pointed out strong evidence indicating that nearly one-third of younger patients will sustain a second ACL injury within the first two years after ACL reconstruction. He postulates that delaying return to sport for two years after ACL reconstruction will significantly reduce secondary ACL graft injuries. According to [PERSON] et al. [25], an accelerated (<10 months) return to sport after ACL reconstruction may be implicated in developing knee osteoarthritis development. In our opinion, return to sport after ACL reconstruction should individually be assessed based on several factors, where MRI is only one of those:  
* Psychological readiness for sport;
* No pain;
* Clinically stable knee (Lachman test, Rollimetr/KT 1000);
* Minimum ROM 0-130;
* MRI--good signal of the graft;
* Biomechanical evaluation: symmetrical muscle strength (on the level of pelvis and knee), good proprioception, movement analysis of simple jump and landing (always paying attention to pelvic stability and valgus knee position). If it is not possible to do an evaluation in the professional lab, a simple, functional test and video analysis based on a cell-phone would also work.