Orthopedic Mechanophenotype: A Structured Narrative Review of Multiscale Biomechanics, Mechanotransduction, and Clinical Decision-Making.

Orthopedic disorders are still classified mainly by anatomy or end-stage morphology, yet osteoporosis, osteoarthritis, fracture nonunion, spinal degeneration, and bone-implant interface failure share a common mechanobiological logic: external load is filtered by hierarchical tissue architecture, converted into cell-scale signals, and integrated with inflammation, metabolism, and repair capacity to determine whether adaptation or failure occurs. This structured narrative review synthesizes recent evidence on multiscale biomechanics, finite element analysis (FEA), mechanotransduction biology, tissue engineering, and emerging digital-twin approaches. Rather than introducing a separate disease entity, we define the orthopedic mechanophenotype as a clinically oriented integrative framework that describes the disease-relevant state generated by three interacting axes: load exposure, tissue susceptibility, and biological adaptability. We summarize how this three-axis state differs across bone, articular cartilage and the osteochondral unit, the intervertebral disc, fracture repair, and bone-implant interfaces. Particular emphasis is placed on evidence hierarchy, model assumptions, and persistent uncertainties, including timescale mismatch, idealized boundary conditions, incomplete cross-scale validation, and overinterpretation of cell-level causality from organ-level surrogates. We further illustrate how mechanophenotyping can be integrated with existing clinical pathways for osteoarthritis load redistribution, fracture fixation and rehabilitation, and spinal or implant-related planning. The central argument is that future progress will depend less on accumulating isolated mechanical variables and more on validated cross-scale markers that connect real-world loading, patient-specific structure, and stage-dependent biology to actionable orthopedic decisions.