Plant-Derived Bioactives in Tendon and Enthesis Biology: An Evidence-Tiered Narrative Review

Tendon injury, tendon-bone interface disruption, and rotator cuff pathology involve inflammatory signaling, oxidative stress, extracellular matrix turnover, cellular senescence, and impaired differentiation. Plant-derived bioactive compounds, including curcumin, quercetin, and other flavonoids and botanical formulations, have been investigated across these pathways in preclinical tendon and enthesis models, but interpretation is complicated by heterogeneous models, formulations, delivery platforms, and endpoints. This review distinguishes preclinical and formulation-specific tissue-response signals from evidence sufficient to support patient-facing clinical or nutraceutical claims. It synthesizes 31 articles using an evidence-tiering framework separating preclinical plausibility (Tier 3), limited human-facing translational evidence (Tier 2), and robust clinical efficacy (Tier 1). The corpus was predominantly Tier 3, with two Tier 2 articles providing human tissue or clinically oriented evidence and no Tier 1 evidence identified. An evidence-calibrated translational proximity map and an overclaim prevention checklist are provided to guide interpretation. The proposed proximity map reflects relative translational position within a focused narrative corpus and was not based on systematic review methods, formal risk-of-bias assessment, or clinical intervention evidence. The limited human-facing evidence does not represent patient-intervention evidence and does not support clinical, supplementation, or treatment recommendations. These compounds remain candidates for staged translational investigation rather than established interventions.