From Diagnosis to Mechanical Objective: Rethinking Foot Orthotic Prescription

Why diagnosis should begin the clinical reasoning process—not determine the orthosis

A patient presents with plantar heel pain.

Another presents with medial tibial stress syndrome.

A third has hallux rigidus.

In each case, it can be tempting to move quickly from diagnosis to prescription:

Plantar heel pain, foot orthosis MTSS , control pronation, Hallux rigidus, Morton’s extension

But is the diagnosis alone really enough information to design an appropriate foot orthosis?

I would argue that it is not.

A more useful clinical question is:

What mechanical problem, if any, am I trying to influence in this particular patient?

That question changes foot orthotic prescription from a product-selection exercise into a process of clinical reasoning.

Does diagnosis determine foot orthotic prescription?

Diagnosis is essential.

It helps identify the clinical condition, consider differential diagnoses and develop an appropriate overall management plan.

But diagnosis alone does not tell us exactly how an orthosis should be designed.

Two patients with the same diagnosis may have very different activity demands, footwear, tissue capacity, joint mobility, loading patterns, occupational requirements and rehabilitation needs.

Their orthotic requirements may therefore also be different.

Interestingly, a 2025 retrospective analysis of 1,000 custom foot orthosis prescriptions found substantial consistency between prescription characteristics and diagnostic categories. The authors also reported that 58% of prescriptions were identical between the left and right feet, raising interesting questions about the individualisation of orthotic prescription.

This leads to an important question:

Are we prescribing for the diagnosis—or for the individual patient in front of us?

Define the mechanical objective before prescribing

Before deciding on shell material, heel-cup depth, posting, skive, extension or accommodation, I find it useful to ask:

What exactly do I want this orthosis to do?

The answer should be reasonably specific.

For one patient, the objective might be to redistribute focal plantar pressure beneath a symptomatic metatarsal region.

For another, it may be to modify the mechanical environment around symptomatic plantar tissues while rehabilitation progresses.

For a patient with a structurally restricted and painful first metatarsophalangeal joint, the objective may be to reduce painful motion demand during propulsion.

For another patient, the objective may simply be to improve comfort sufficiently to maintain walking, work or sporting activity.

Once the objective is clear, the individual components of the prescription should have a reason for being there.

Rather than:

Diagnosis → Orthosis

I prefer:

Clinical assessment → Mechanical interpretation → Mechanical objective → Orthotic design → Patient response → Review

Give every foot orthosis a job

I often describe this clinically as giving the orthosis a job.

If I prescribe a deeper heel cup, why?

If I add a medial heel skive, what am I attempting to influence?

If I use a metatarsal dome, what loading pattern am I trying to modify?

Why have I selected a particular shell stiffness?

Why am I using a Morton’s extension rather than a Reverse Morton’s extension?

Every significant component should relate to something identified during the clinical reasoning process.

If we cannot explain why a modification is present, perhaps we should reconsider whether it needs to be there.

This does not mean that every proposed mechanical effect is scientifically proven.

That distinction is important.

A recent paper examining the relationship between custom foot orthosis research and clinical practice highlighted the difficulties created when standardised research protocols are compared with the more individualised prescriptions used clinically. The authors call for closer collaboration between researchers and clinicians and research approaches that better represent real-world orthotic prescription.

For clinicians, this means being clear about the distinction between:

Published evidence

Biomechanically plausible clinical hypotheses

and

Experience-informed clinical decision-making

These can all contribute to practice, but they should not be presented as though they carry the same level of evidence.

Why more orthotic correction is not always better

One of the potential traps in foot orthotic prescription is assuming that if a small mechanical intervention is useful, a larger intervention must be better.

That is not necessarily the case.

The most mechanically aggressive orthosis is not automatically the most clinically effective orthosis.

The patient has to wear it.

It needs to fit their footwear.

It needs to be sufficiently comfortable.

And most importantly, it needs to contribute to an outcome that matters to the patient.

This leads to a principle I use frequently in clinical practice:

Use the minimum effective intervention.

If a relatively simple modification achieves the clinical objective, why automatically add more?

If a prefabricated device can achieve the required objective, does that patient necessarily need a custom device?

If a relatively small modification produces an acceptable clinical response, why increase it simply because a larger modification is technically possible?

Orthotic complexity should follow clinical need—not habit.

Test the mechanical hypothesis

An orthotic prescription can also be viewed as a clinical hypothesis.

We assess the patient.

We identify findings that appear relevant.

We develop a hypothesis about the mechanical environment contributing to the patient's presentation.

We then introduce an intervention intended to influence part of that environment.

Where practical and clinically appropriate, I like to test elements of that hypothesis before or during prescription.

This may involve temporary padding, wedging, taping, footwear modification or another appropriate clinical trial.

The patient's response may provide useful information about whether the proposed intervention is comfortable and whether it produces the functional response we anticipated.

However, there is an important limitation:

An immediate response is not proof of long-term treatment success.

It is information.

That information should become one part of the wider clinical decision-making process.

A foot orthosis is not the whole treatment plan

An orthosis may influence part of the patient's mechanical environment.

It does not automatically address everything contributing to the presentation.

A runner may still require load modification and progressive return to activity.

A patient with reduced muscular capacity may require strengthening.

Someone wearing inappropriate footwear may require footwear advice.

Mobility, strength, recovery, occupation, training error and general health may all be relevant depending on the individual presentation.

The orthosis should therefore sit within the management plan rather than becoming the management plan.

This principle is particularly relevant in conditions such as plantar heel pain, where contemporary management increasingly considers orthoses alongside exercise, education and other interventions rather than viewing a device as a universal standalone treatment.

Why orthotic review matters

I do not consider an orthotic prescription finished when the device is dispensed.

Review is part of the prescription.

At follow-up, we should return to the original clinical objective.

Has pain improved?

Has walking tolerance increased?

Can the patient work for longer?

Can they run further?

Has confidence in activity improved?

Is the device comfortable?

Does it fit the footwear the patient actually wears?

Has rehabilitation progressed?

Have any new symptoms developed?

And perhaps most importantly:

Did the orthosis do the job we prescribed it to do?

If yes, we may maintain the prescription.

If partly, we may modify or simplify it.

If not, we should reconsider the prescription—and sometimes reconsider our original mechanical hypothesis.

Changing a hypothesis in response to the patient's outcome is not treatment failure.

It is clinical reasoning.

From biomechanics to better clinical decisions

Foot biomechanics can become complicated very quickly.

Angles, axes, moments, forces, joint positions and plantar-pressure patterns are all interesting.

But ultimately, they are useful only when they help us make better clinical decisions for the individual patient.

The aim of foot orthotic therapy should not simply be to make a foot appear more “normal”.

Nor should every biomechanical finding automatically become something that needs correcting.

Instead, before prescribing, I believe we should ask:

Is this finding relevant to the patient's problem?

Can I realistically influence it?

What mechanical objective am I trying to achieve?

What is the minimum intervention required?

How will I know whether it worked?

These questions make orthotic prescription more transparent, testable and clinically meaningful.

Ultimately:

Patients don't come to us because they need orthoses. They come because they want to move with less pain, greater confidence and better function.

Everything else should serve that objective.

The Keep Moving Guide to Clinical Decision-Making in Foot Orthosis Prescription

This article is the first in my Keep Moving Biomechanics series and introduces some of the clinical reasoning principles explored in my forthcoming book:

The Keep Moving Guide to Clinical Decision-Making in Foot Orthosis Prescription: From Assessment to Prescription

The book is being developed as a practical resource for podiatrists, physiotherapists and MSK clinicians, exploring the journey from patient assessment and biomechanical interpretation through to mechanical objectives, orthotic design, clinical testing and structured review.

Rather than providing a list of diagnoses and corresponding orthoses, the book focuses on an important question:

Why am I prescribing this particular orthosis for this particular patient?

Publication details coming soon.

About the author

Abdulrhman Saleh, BSc (Hons) Podiatry is an HCPC-registered musculoskeletal podiatrist and clinical educator based in Manchester, UK.

His clinical interests include lower-limb biomechanics, foot orthoses, musculoskeletal podiatry and rehabilitation.

Keep Moving Podiatry . Manchester, UK www.keepmovingpodiatry.uk

References:

1. Jackson A, Sheerin K, Reid D, et al. Custom Foot Orthoses: A Retrospective Analysis of 1000 Prescriptions From New Zealand Podiatrists. Journal of Foot and Ankle Research. 2025;18(2):e70044.

2. Moisan G, Chicoine D, Griffiths I, Robb K. Bridging the gap between custom foot orthoses research and clinical practice. The Foot. 2025;63:102177.

3. Thomas MJ, Hughes G, Cooke K, et al. Clinical and cost-effectiveness of individualised exercises and foot orthoses in the treatment of plantar heel pain: protocol for the TREADON randomised multi-arm multi-stage adaptive trial. NIHR Open Research. 2025.