 The timing of return to play is one of the most critical decisions made following ACL reconstruction. Returning too early carries the risk of graft failure, while returning too late could cost patients financial and athletic opportunities. Unfortunately, no universal objective method exists to determine the best time for athletes to resume full activities. But according to a new study reported in the American Journal of Sports Medicine, such methods could be on the horizon with the help of MRI technology. One promising marker for estimating the best time for athletes to return to play is ACL graft maturation. That's the process by which a surgical graft makes the transformation from tendon tissue into a substance similar to a normal ACL. The problem is that this transformation is difficult to track over time. Tissue biopsies are currently the gold standard, but are invasive and, in most cases, impractical to perform. And conventional MRI, although not invasive, can't easily resolve features with low water content, such as ligaments and tendons, at least not without some refinements. Ultra-short echo time MRI imaging allows for visualization and quantification of tendon grafts through a property known as T2-STAR. T2-STAR is a signal decay property of imaged tissue that is insensitive to variations between MRI scanners. As such, measurement of T2-STAR could provide direct, objective, and quantifiable evidence of ACL graft remodeling that can't be generated with the long echo time sequences of conventional MRI. To test this approach, researchers mapped changes in T2-STAR in 12 patients who underwent primary ACL reconstruction with an autographed. T2-STAR MRI scans were performed at 1, 3, 6, 9, and 12 months after surgery. Among the 10 patients who completed the study, T2-STAR values showed a statistically significant increase of 82% between months 1 and 6, followed by an approximately 19% decline between months 6 and 12. A similar trend was observed for the mean ratio of T2-STAR values between injured and intact tissue. Additionally, changes in T2-STAR values appeared to vary from one region to another. Collectively, the results suggest that T2-STAR values could be sensitive to changes tied to the maturation of ACL grafts. One limitation of the study is that the intact ACL of the contralateral knee was only imaged one month after surgery. Imaging at the same time points as the reconstructed knee would have allowed for the detection of tissue changes within the intact ACL that may have altered the calculated T2-STAR ratios. Future studies could help researchers gain insights into the status of ACL grafts following surgery and improve clinicians' ability to noninvasively and objectively assess graft maturity before athletes return to play.