MRI Features of Acute Muscle Injuries in Professional Soccer Players: A Systematic Review of Prognostic Associations With Return to Play

<b>BACKGROUND.</b> In professional soccer players, muscle injuries are a primary cause of loss of time from competition and have high recurrence rates, thus posing management challenges. MRI is widely used for injury grading and prognosis, yet associations of MRI findings with timelines for return to play (RTP) have been inconsistent. <b>OBJECTIVE.</b> The purpose of this study was to evaluate prognostic associations with RTP duration of MRI features of acute muscle injuries in professional soccer players. <b>EVIDENCE ACQUISITION.</b> A systematic review of the PubMed and Scopus databases was performed for studies conducted from January 2014 to February 2025 evaluating an MRI classification system for acute muscle injuries in professional soccer players and providing a quantifiable RTP outcome. Extracted information was summarized through narrative synthesis, organized according to muscle group. <b>EVIDENCE SYNTHESIS.</b> The analysis included 12 studies that evaluated a total of 961 acute muscle injuries in professional soccer players, all of whom were male. In seven studies of hamstring injuries, tendon involvement (particularly of the free tendon of the biceps femoris) and musculotendinous junction involvement were key findings for predicting prolonged RTP; edema had poor predictive utility. In addition, injury grades based on two different advanced MRI classification systems showed weak and moderate prognostic associations with RTP. In four studies of quadriceps injury, distal aponeurosis involvement and associated hematoma were key findings for predicting prolonged RTP beyond structural grades alone. In two studies of adductor injuries, intratendinous location, large muscle gap, and proximal injury site were key findings for predicting prolonged RTP. In one study of hip external rotator injuries, such injuries were generally mild, exhibiting a low structural grade on MRI, and were associated with favorable prognosis (i.e., prompt RTP). In two studies of calf injuries, injury grade and extent of edema were key findings for predicting prolonged RTP. However, most calf muscle reinjuries occurred within 2 months of RTP, commonly after low-grade injuries. <b>CONCLUSION.</b> The findings highlight the role of MRI in prognostic assessments across muscle groups in professional soccer athletes with acute muscle injury. <b>CLINICAL IMPACT.</b> MRI is an important, yet not stand-alone, component of the RTP decision-making process. Imaging, clinical, and functional criteria should be combined to inform RTP decisions.