From linear rehabilitation to graded stress exposure: A clinical framework for return to sport after anterior...

Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction remains associated with a substantial risk of reinjury despite advances in surgical techniques and rehabilitation protocols. Contemporary rehabilitation strategies primarily focus on restoring strength, range of motion, and neuromuscular control under controlled conditions. However, emerging evidence suggests that performance in standardized functional tests does not necessarily reflect an athlete's ability to tolerate the dynamic, unpredictable, and cognitively demanding environment of competitive sport.

To develop a clinically applicable decision framework that operationalizes graded-stress exposure and provides phase-specific criteria for progressing athletes from controlled rehabilitation to unrestricted sport-specific participation after ACL reconstruction.

A narrative synthesis approach was conducted integrating current evidence from ACL rehabilitation, neuromuscular control, motor learning, ecological dynamics, and injury prevention literature. Key limitations of traditional linear rehabilitation models were identified and used to develop a current concept structured around progressive exposure to sport-relevant stressors.

A four-domain stress exposure model was developed, consisting of: (1) mechanical load, (2) movement variability, (3) external perturbation, and (4) decision-making speed. These domains were integrated into a four-phase rehabilitation framework: (I) tissue protection and motor reactivation, (II) controlled load development, (III) progressive stress exposure, and (IV) sport-specific chaos simulation. For each phase, the framework links observable stress-exposure parameters to progression decisions, allowing clinicians to identify the domain limiting advancement and to selectively increase, maintain, or regress task complexity. This approach addresses the mismatch between conventional rehabilitation settings and real sport demands, which may contribute to persistent neuromuscular deficits and reinjury risk.

The proposed graded stress-exposure framework complements established RTS criteria by translating mechanical, neuromuscular, and neurocognitive stress domains into phase-specific progression decisions, allowing clinicians to identify the domain limiting rehabilitation advancement and guide selective progression or regression of rehabilitation demands before unrestricted sport participation. Prospective validation is required to determine whether this decision-based approach improves functional outcomes or reduces reinjury.

Level V, current concept.