Ninety-six patients who had undergone ACL reconstruction were randomized to receive either a theory-driven mHealth intervention via a smartphone app called “ACL-Well” in addition to standard care (n=41), or standard care alone (n=55). The primary outcome was post-surgical recovery, measured via knee muscle strength, knee laxity, and subjective knee evaluation at 4 months. Secondary outcomes included self-reported rehabilitation adherence, treatment motivation, and social cognition constructs, assessed at baseline, 2 months, and 4 months. Overall, the results of the study revealed no significant between-group differences in recovery outcomes (p = .25 to .99). However, the intervention group showed better maintenance of treatment motivation and adherence, especially in participants with initially lower baseline levels. These findings suggest that while the mHealth app did not improve clinical recovery outcomes, it may help sustain psychological and behavioral engagement during rehabilitation.