How Early Is Early? Defining Functional Rehabilitation After Acute Achilles Tendon Rupture: A Narrative Review.

Early functional rehabilitation after acute Achilles tendon rupture is increasingly used in nonoperative protocols, but the definition of "early" remains highly heterogeneous across the literature and no standardized timing threshold has been established. This narrative review clarifies the conceptual and operational definitions of early rehabilitation and examines the unresolved timing-threshold problem. Existing evidence supports early functional rehabilitation without a demonstrated increase in rerupture risk compared with delayed immobilization. Early rehabilitation may improve short-term functional recovery; however, clear long-term superiority over more delayed strategies has not been demonstrated. Substantial heterogeneity persists in the initiation of weightbearing and range of motion and in orthosis duration. Although weightbearing within four weeks is commonly used as an operational definition of early rehabilitation for evidence synthesis, it is not a biologically or clinically validated threshold. The literature also lacks granular evidence defining a timing-response relationship or an optimal initiation window. Current evidence therefore supports early functional rehabilitation as a reasonable strategy, but future research should identify validated timing-response relationships and patient-specific strategies.