In vivo animal models of Achilles tendon rupture management: a narrative review.

INTRODUCTION: Acute Achilles tendon rupture is common, and the balance between surgical and non-surgical management remains contested. Much of the mechanistic evidence informing this debate derives from in vivo animal models, which have not previously been appraised together as a class. SOURCES OF DATA: PubMed/MEDLINE was searched using terms for the Achilles/calcaneal tendon combined with terms for rupture, transection, tenotomy, defect, repair and relevant animal species. Reference lists of included studies and pertinent reviews were hand-searched, supplemented by a grey-literature/web sweep. The search was last updated in June 2026. Given the marked heterogeneity of species, injury model, intervention and outcome measures, findings are synthesized narratively rather than pooled quantitatively or scored against a structured risk-of-bias instrument. AREAS OF AGREEMENT: Twenty-four in vivo studies (predominantly rat, with mouse, rabbit and one sheep model) were identified. Immobilization angle and duration, rather than repair per se, appear to be dominant determinants of early healing. Biological and pharmacological augmentation strategies generally improve biomechanical properties, with less consistent histological change. AREAS OF CONTROVERSY: Controversies in this literature are of two kinds, substantive and methodological. Direct comparisons of repair versus non-repair are scarce, and reach divergent conclusions once immobilization is accounted for. Reporting of randomization, allocation concealment, blinding and sample-size justification is inconsistent and often absent. GROWING POINTS: Cell- and vesicle-based therapies, engineered scaffolds and lineage-tracing/mechanistic models are actively reshaping this literature. AREAS TIMELY FOR DEVELOPING RESEARCH: Consensus reference models with standardized transection, repair and immobilization protocols, explicit reporting of ankle angle, duration and method of immobilization, weight-bearing status and timing of mobilization, ARRIVE-compliant reporting, and embedding of biological augmentation within defined management models are needed to strengthen translational value.