Internal musculoskeletal loads, e.g., the muscle, ligament, and joint-contact forces that are central to orthopaedic function, injury, and disease, cannot be measured noninvasively in vivo owing to ethical or technological limitations. They must instead be inferred by combining experimental measurements with computational modelling: experiments supply the measurable inputs, namely subject-specific anatomy, joint motion, and external loading, while computation recovers the internal forces that no sensor can measure. However, each contributing discipline has tended to capture only part of this picture. Clinical orthopaedic assessment largely focuses on morphology, whereas conventional motion analysis measures only rigid-body kinematics. Computational or mathematical mechanical models can estimate internal loads but have been constrained by a lack of in vivo, subject-specific inputs, relying instead on generic or idealised geometry and motion. This lecture traces a combined experimental and computational pipeline that turns still medical images into living, load-bearing models, and argues that artificial intelligence is the enabling layer that makes these models subject-specific, accurate, and clinically deployable at scale.
The central aim has been to integrate three facets of the musculoskeletal system that are conventionally examined in isolation, namely its morphology, its motion, and its function, or mechanics, within a single subject-specific framework, and the resulting pipeline is presented as a progression from pixels to forces. Deep-learning segmentation and statistical shape modelling reconstruct subject-specific bone and joint geometry from CT, MRI, and even single planar radiographs; AI-accelerated model-to-image registration of fluoroscopic sequences recovers three-dimensional joint motion to sub-millimetre and sub-degree accuracy; and these geometries and motions drive subject-specific musculoskeletal and finite-element models that estimate the muscle, ligament, and joint-contact forces underlying normal and pathological movement. To the authors’ best knowledge, the integration of these components into a single image-to-force workflow represents a distinct departure from the generic, scaled-model approaches that dominate the field.
Applications across joint degeneration, surgical reconstruction, and sports injury illustrate how computational mechanics, so framed, converts routine clinical images into actionable mechanical insight. It is hoped that this image-driven, AI-enabled approach will help bridge computational mechanics and translational orthopaedic care.