Biomechanical engineering studies human motion, forces and the physical design of devices that interact with the body. A prosthetic foot can pass an appropriate mechanical strength test while the complete fitted device still requires assessment of real movement and suitability for its intended user.
This guide explains gait and force measurement, static and cyclic loading, tissue mechanics, prosthetics, modelling, biological safety, usability and medical-device evidence. It distinguishes the current ISO 10328:2016 from its unpublished replacement and includes ISO 22675:2024 and ISO 10993-1:2025.
It complements Biomedical Engineering, Human Factors Engineering, Materials Engineering and the Engineering Gold Standard hub.
What must biomechanical engineering actually demonstrate?
- Define the real movement and intended user population before modelling loads.
- Distinguish directly observed forces or motion from internally modelled quantities.
- Verify static strength, repeated loading and product configuration where appropriate.
- Evaluate body contact, usability and medical risks separately from structural performance.
- Reserve individual device selection and clinical decisions for qualified professionals.
Find the question behind the biomechanics
1. A prosthetic foot that passes a test still needs a real person
A manufacturer tests a prosthetic foot under a specified loading sequence, and the component passes its structural requirements. The result is important. Yet a particular user may still have difficulty walking comfortably or safely with the final assembled device because fit, alignment, body mechanics and daily activities affect the outcome. A successful laboratory specimen does not automatically establish suitability for every person’s movement.
Biomechanical engineering studies forces, motion, deformation and physical interactions in the human body and related devices. It spans gait analysis, orthopaedic design, rehabilitation engineering, sporting equipment, musculoskeletal modelling and assistive technologies. Its questions depend on anatomy, movement and intended purpose rather than treating people as identical mechanical test fixtures.
The gold standard is not the stiffest implant, lightest prosthesis or best-looking motion diagram. It is credible physical evidence matched to the real human task, with design and safety requirements, appropriate testing, qualified clinical assessment where needed and responsibility for continued use.
2. Define the actual movement before modelling it
Walking, climbing stairs, lifting objects, maintaining balance and manipulating tools have different mechanical demands. A design that performs well during one repeatable laboratory action may be less suitable for a more complex user task. The engineering brief should define the intended use, relevant population, environment and consequences of undesirable performance.
Clinicians, users and engineers may see different parts of the problem. Engineers can describe forces and structural limits, while clinicians evaluate functional goals, health conditions and the overall suitability of an intervention. A successful design respects these different forms of expertise and does not convert one mechanical test into an individual clinical prescription.
A device intended for a narrow use should describe its limits explicitly. A promising early prototype is useful information, but a broader product claim requires appropriate evidence for the population and conditions being promised.
3. Motion capture describes movement, not automatically its cause
Motion cameras and wearable sensors may estimate position, angles and movement over time. These measurements help describe a gait or other task, but their accuracy depends on sensor placement, markers, reference frames and the algorithms applied. Joint motion inferred from surface measurements may be affected by soft-tissue movement and modelling assumptions.
An engineer should distinguish the captured trajectory from underlying joint or muscle forces. Two people can make apparently similar movements while their internal loads or physical constraints differ. Movement data alone cannot reveal every pain, fatigue or neurological cause.
The Instrumentation Engineering guide explains how an accurate sensor may observe an incomplete physical quantity. Biomechanics adds the difficulty that human tissues and movement strategies are complex and variable.
4. Force plates measure external interaction, not every internal joint load
Force platforms can provide information about contact forces and moments between a person and a supporting surface under defined conditions. That can help analyse loading patterns during walking, running or jumping. The measured external forces still require appropriate models to infer internal effects, and a model may depend on individual anatomy and movement assumptions.
A maximum external force should not automatically be interpreted as the exact load on one ligament, bone or prosthetic component. Multiple body structures contribute to distributing forces, and peak quantities may occur at different times. Relevant clinical interpretation demands context and professional expertise.
Quality depends on appropriate instrument reference, timing, coordinate systems and matching motion observations to force data. A beautifully smooth force curve is not evidence that all related calculations are valid.
5. Static strength and cyclic durability answer separate questions
An external prosthetic component may resist one large applied force yet behave differently after repeated loading. Strength and durability therefore need appropriate forms of evidence. Different test methods examine different conditions and cannot be treated as a universal simulation of every human activity.
ISO 10328:2016 remains the published standard for structural testing of lower-limb prostheses as of 18 October 2026. A third edition entered the under-publication phase on 3 October 2026 and has not yet replaced it. The current document distinguishes static and cyclic strength testing and includes an important warning that the standard is not a guide for choosing a device for an individual person.
Professional product and clinical decisions should therefore keep technical conformity and personal suitability separate. A test can establish important structural performance without answering whether the device is right for a particular user.
6. Prosthetic foot tests should represent the intended loading purpose
An ankle-foot device experiences changing loads during the stance phase of gait. A test that captures only one fixed load may fail to represent the sequence of mechanical conditions important to a design. The appropriate standard depends on the product and the physical characteristic being verified.
ISO 22675:2024 specifies test methods for prosthetic ankle-foot devices and foot units, including cyclic testing intended to simulate relevant loading characteristics from heel strike toward toe-off. It was published in December 2024 and replaces the older edition. The method provides defined evidence, not a personalised fitting protocol.
Manufacturers should identify the tested assembly, configuration, load class where applicable and limitations. If production changes a material or critical connection, the engineering team must decide what earlier evidence remains valid.
7. Material selection is about interaction with the body and service
Biomechanical designs may contain metals, polymers, composites, textiles or other materials, chosen for appropriate strength, stiffness, durability, weight and practical use. A material that behaves well under a mechanical test can create different concerns through wear, surface condition, environmental exposure or contact with tissues. Suitability depends on the whole intended application.
Materials also change during manufacturing and service. The properties of a finished component may differ from a sample of raw stock, and joints can become dominant mechanical features. Engineers need product-specific evidence rather than a claim that one material is always the best choice.
The Materials Engineering guide explains how nominal grades differ from in-service properties. Biomechanics extends that reasoning to human interaction and the importance of comfort, fit and safety where relevant.
8. Biocompatibility is not proved by calling a material medical grade
Some biomechanical devices contact skin or internal tissues. Their biological safety depends on intended contact, exposure duration, composition, processing, degradation and other application-specific factors. A product may be strong and mechanically reliable while requiring separate evaluation of biological risks.
ISO 10993-1:2025 is the current published sixth edition for biological evaluation of medical devices. It aligns evaluation of biological safety with the risk-management process and replaces the 2018 edition. It does not assert that every nominally compatible material becomes safe in any device or for any exposure.
Qualified regulatory and clinical specialists should determine what evaluation is necessary for a particular product. The outcome cannot be borrowed from another device merely because both share a material name.
9. Soft tissue creates modelling problems unlike a steel beam
Human tissues can display complex, time-dependent and direction-dependent mechanical behaviour. Their properties may vary among individuals and conditions, while geometry and loading are difficult to observe fully. A simple elastic engineering approximation can be useful for a narrow purpose and misleading outside its validation range.
A computational study should explain which anatomy, material behaviour and boundary conditions are represented. A model of a healthy adult joint is not automatically appropriate for a different patient population or an altered anatomy. Medical data and assumptions need careful handling and appropriate privacy and ethical governance.
An apparently precise tissue stress map cannot substitute for real-world evidence of safety or function. The Computational Engineering guide details why a correctly solved model may still represent the wrong physical problem.
10. Musculoskeletal models need credible inputs and independent checks
Engineers may estimate muscle and joint mechanics by combining anatomy, kinematics, external forces and mathematical assumptions. Such models can help compare design alternatives or identify where further experiments would be useful. Their outputs remain estimates based on a defined representation of the human body, not direct measurements of every internal force.
Prediction credibility depends on input quality, model structure and evidence that supports its intended use. When multiple plausible models fit the observed motion, a single preferred estimate should be reported with limitations and relevant sensitivity. A subject-specific model may require additional information not available from a general motion analysis.
The FDA’s November 2023 final guidance provides a risk-informed framework for credibility of physics-based computational models used in medical-device submissions. It is U.S. regulatory guidance rather than a universal certificate for every biomechanics model.
11. Personalised designs must preserve technical approval evidence
Customised supports, prostheses and other devices may be designed around an individual’s geometry or activity. This can improve fit for some users, but it also creates questions about which aspects of a previous product test remain representative. A design change may affect a critical component or change the physical limits previously demonstrated.
Engineering records should identify the approved design, manufacturing route, materials, relevant testing and any boundaries within which customisation is permitted. A 3D scan can provide useful geometry while omitting properties such as tissue tolerance, dynamic loading or expected use. Shape matching is not a complete safety argument.
The Additive Manufacturing Engineering guide discusses design-to-part traceability. In a medical or assistive application, qualification and clinical suitability add further requirements.
12. A rehabilitation device is tested with users, not just a fixture
An assistive device may meet mechanical and electronic specifications while remaining difficult to put on, adjust, clean or use in daily activity. Its intended users may differ in mobility, strength, cognition and the environments where the device is needed. Testing only with experienced development staff can miss important use-related problems.
Representative evaluation should consider appropriate users, tasks, fit, comfort and safe interaction under qualified conditions. A device designed for one user population may not be valid for another without further evidence. Human-factors work is especially important where a user must recognise limitations or respond to an unusual device state.
The Human Factors Engineering guide explores these interfaces. Biomechanical engineering provides the physical evidence needed to understand loads, movement and repeated service within that wider user experience.
13. Risk management should follow both mechanical and human consequences
Mechanical failure can be important, but risks may also arise through fit, skin contact, incorrect interpretation, changed user capability or service and maintenance. The appropriate evaluation depends on the product and intended use. A low likelihood assigned without relevant evidence does not settle a high-consequence concern.
ISO 14971:2019 remains the published medical-device risk-management standard, confirmed in 2025. It addresses identifying hazards, evaluating risk, applying controls and learning from production and post-production information. Biomechanical products regulated as medical devices must be assessed through their applicable obligations.
The analysis should distinguish an engineered safeguard from a warning that merely shifts responsibility to the user. Serious limitations need clear communication and an approved plan for responding when a defect or mismatch is identified.
14. Singapore medical-device requirements depend on the actual intended use
Not every sports sensor, training device or research apparatus is regulated as a medical device in the same way. Intended claims and legal classification determine the relevant requirements. A prosthetic component marketed for medical use can face different regulatory and clinical obligations from a nonmedical movement-analysis tool.
Singapore HSA’s medical-device guidance library was updated on 10 September 2026. It lists GN-15-R14 for product registration and GN-20-R2 for clinical evaluation, among other documents. These references help manufacturers identify their obligations, but decisions depend on the device, risk class and current applicable regulations.
An engineering report should distinguish bench performance, clinically relevant evidence, product registration and a practitioner deciding suitability for an individual. None automatically replaces the others.
15. Manufacture and supply must reproduce the approved mechanical state
Mechanical performance depends on actual materials, dimensions, assembly and process history. A prototype built by a specialist can pass testing while later production units differ through tooling, suppliers or manufacturing variation. An acceptable production programme needs evidence that the delivered parts retain the critical requirements.
Testing and inspection should be matched to the relevant properties and configuration. A material certificate and a visual inspection may be useful while failing to address a difficult hidden feature or long-term cyclic behaviour. The required approach depends on intended application and consequence.
The Engineering Quality Assurance Services guide connects requirements to actual delivered units. In biomechanics, that chain must also respect variation in human use and any medical-device production obligations.
16. Biomechanical measurement needs consistent reference frames
Joint angles, ground reaction forces and positions are reported in coordinate systems and at defined times. Mixing left and right, local and global reference frames, or signals that are not time-aligned can produce misleading interpretation even when the instruments individually function. A result must describe exactly which measurement and transformation created it.
Data quality includes correct participant and device identities, suitable sample conditions, instrument uncertainty and appropriate processing. Averaging several participants may conceal an important difference in individual movement. Equally, selecting only the most favourable trial may exaggerate the product’s claimed effect.
A trustworthy laboratory preserves raw data, relevant calibration, approved protocols and the analysis version so another qualified reviewer can reproduce the interpretation. The shape of a graph alone cannot certify a medical or sporting outcome.
17. Service, changes and real-use feedback complete the engineering cycle
Prostheses, orthoses and other devices may be modified, serviced or replaced during use. A new component can alter fit or the loading of another part even when it appears mechanically compatible. The original acceptance evidence may need qualified reassessment after material, geometry, software or user circumstances change.
Complaints and performance observations can reveal problems not captured by the original laboratory tests. The appropriate response depends on severity, device status and the roles of clinicians, manufacturers and regulators. An engineering team should investigate systematic findings rather than dismiss them as user error.
The Engineering Asset Integrity Services guide explains condition-to-action governance, while the Biomedical Instrumentation Engineering guide covers patient-related measurement evidence. Biomechanics adds physical fit, loads and motion.
18. The biomechanical gold standard is a safe function that people can actually use
Biomechanical engineering succeeds when its measurements and models explain real movement sufficiently to support a justified design. A device may be technically sophisticated and strong yet unsuitable for some intended tasks or users. Validity depends on the combination of mechanical evidence, usability and the applicable clinical or legal requirements.
Review the full chain: intended motion, user population, actual material and geometry, static and cyclic tests, data quality, model credibility, human evaluation, regulatory requirements and maintenance. The engineer should be able to distinguish a proven general product characteristic from a claim that requires personal clinical assessment.
The gold standard is not selecting the strongest limb or the most persuasive force curve. It is engineering evidence that respects human variability and supports the right people, devices and clinical professionals in making safe, informed choices.
Worked case: a passed prosthetic component test and an incomplete user journey
This is a fictional medical-device development case, not a real patient assessment or clinical prescription. A prosthetic foot component passes its required structural testing. During representative user evaluation, some participants have difficulty performing a specific everyday task with the assembled device. The engineering team should investigate whether the issue arises from the device’s design limits, the assembled configuration, measurement methods or usability; clinical specialists must independently judge suitability for individual users.
| Evidence | What it establishes | What it cannot establish by itself |
|---|---|---|
| Static strength test passed | Resistance under defined structural test conditions | All repeated-load and real-world functional performance |
| Cyclic test passed | Performance under specified repeated loading | That the component is suitable for every user or terrain |
| Motion-capture graph is smooth | Estimated movement under measured trial conditions | Every internal load, comfort or clinical consequence |
| Force plate measures contact force | External force in a defined coordinate frame | Exact force at every joint or tissue location |
| Material test passes | Selected mechanical characteristics | Biological safety or assembled device suitability |
| Device is mechanically assembled | Components fit their specified interfaces | Appropriate patient fit and authorised clinical use |
The lesson is to keep engineering verification and individual clinical suitability distinct. The manufacturer should retain appropriate technical evidence for the device and its claimed uses; practitioners evaluate the person, their needs and the permitted options.
Frequently asked questions
What does biomechanical engineering study?
It studies physical forces, motion, material behaviour and interactions of the human body with equipment or medical and assistive devices. It is broader than any single implant or prosthetic technology.
Does a passed prosthetic foot strength test mean it suits every person?
No. Strength and durability testing addresses specified product conditions. Individual fit, activity, function and clinical suitability require separate assessment by qualified professionals.
Which edition of ISO 10328 applies in October 2026?
ISO 10328:2016 remains the published lower-limb prosthetic structural-testing edition. A third edition is under publication but has not yet replaced it.
What is new about ISO 22675?
The current 2024 edition addresses ankle-foot devices and foot units, with testing that represents relevant parts of the loading sequence during walking. Its scope and limitations matter to the acceptance decision.
Does a motion-capture graph directly measure muscle force?
Not necessarily. Motion capture estimates movement; internal forces may require further models, inputs and validation. Such estimates should be labelled as model-based rather than direct observations.
What is the role of ISO 10993-1:2025?
It establishes general principles for biological safety evaluation of medical devices within risk management, for relevant body contact and intended use. It does not replace strength, functional or clinical evaluation.
Current prosthetics, materials and medical-device standards
- ISO 10328:2016 — Structural Testing of Lower-Limb Prostheses (still published in October 2026)
- ISO 10328, Third Edition — Under Publication Since 3 October 2026
- ISO 22675:2024 — Testing of Prosthetic Ankle-Foot Devices and Foot Units
- ISO 10993-1:2025 — Medical Device Biological Evaluation Within Risk Management
- ISO 14971:2019 — Medical Device Risk Management
- U.S. FDA — Computational Modelling and Simulation Credibility in Medical Devices (2023 Final Guidance)
- Singapore HSA — Product Registration GN-15-R14 (September 2026) and Clinical Evaluation Guidance
- eduKate — Computational Engineering
- eduKate — Verification and Validation Services
- eduKate — Additive Manufacturing Engineering
- eduKate — Gold Standard Sectors and Services Directory
Biomechanical engineering related to medical devices, prostheses, orthoses and individual health decisions requires appropriate technical, clinical and regulatory expertise. This educational article is not a prescription, device-fitting guide, rehabilitation plan or authorisation to use a medical product.
The Gold Standard of Biomechanical Engineering
The strongest biomechanical design respects the difference between a physical test, a model and a real person’s needs. It makes a device’s general performance credible without using that evidence to claim more than it proves. Better engineering begins where the human body and the technology actually meet.