The word covers four quite different things, with four quite different evidence bases. Lumping them together is the main reason the field sounds either overhyped or underwhelming depending on who is talking.

1. Consumer devices — watches and phones counting steps, distance and running metrics
2. Sensor insoles — pressure sensors inside the shoe that measure how much load goes through the foot, and where
3. Movement sensors — small units strapped to the leg that track how your joints move as you walk
4. Body monitors — skin temperature and similar readings that can pick up a problem before you can see it

They are worth taking one at a time.

Almost every patient now arrives with continuous data about their own activity. This is genuinely useful, giving an objective picture of what someone actually does rather than what they estimate in clinic, but the accuracy varies more than people realise, and it varies mostly by where the device sits.

One review brought together 77 treadmill studies and grouped the errors by where the device was worn. At normal walking speed, the typical error was:

The device most people own is worn in the least accurate position. At slower walking speeds, which is exactly how people walk after foot and ankle surgery, accuracy typically falls further, because the arm swing a wrist device relies on becomes harder for it to detect.

This is where wearables have moved past promise into demonstrated benefit, in two distinct settings.

Preventing diabetic foot ulcers

An early-stage trial recruited 90 people from UK diabetic foot clinics, all with nerve damage in the feet and a recent ulcer on the sole of the foot. Everyone was given insoles that measured the pressure under the foot throughout the day. Half also received an alert on a linked smartwatch, a sound and a message telling them to take the weight off, whenever pressure built up too high. The other half received no alerts.

This was a small early study rather than a definitive trial, and it was part-funded by the company that makes the device, both worth knowing. But the mechanism is straightforward, the effect size is large, and the outcome measured is one that matters enormously: diabetic foot ulceration is a leading route to amputation.

Monitoring weight-bearing after surgery

This second application deserves attention from anyone who has ever been told to keep weight off a foot.

Eighty-four people with an ankle fracture were given pressure-sensing insoles inside their boot, which recorded their daily steps and how much load went through the foot for six weeks. All were told to keep the weight going through the leg to between 15 and 30 kg. Half received an immediate alert if they went over 20 kg; half received nothing.

The findings were uncomfortable reading:

• Few people in either group managed to stay within the weight limit or keep the boot on
• Putting too much weight through the foot started as early as week one
• Only 10% of those without alerts were still wearing the boot by week three
• Immediate alerts nearly doubled boot use, 57.4% against 29.1%, and helped people stay within the weight limit

That reframes a common clinical assumption. When bones fail to knit together after surgery, “the patient didn’t follow instructions” may be less accurate than “we asked for something that cannot be done reliably without a sensor.”

Measuring the way someone walks has traditionally meant a laboratory with cameras tracking markers on the body: accurate, but expensive, slow and available in few places. Small movement sensors can do a version of the same job in an ordinary clinic room.

These systems used to treat the foot as one solid block, which is a poor description of something with as many joints as the foot. Newer versions look at the back and the front of the foot separately, and testing shows the results hold up whoever takes the measurements and however often they are repeated, with errors of under 5 degrees for up-and-down and rotational movement. Measuring how far the foot tilts inwards or outwards is still less reliable, which matters, because that is the direction in which much foot deformity happens.

In foot drop, these sensors give very consistent results when the test is repeated. The timing of each stage of a step, and the number of steps per minute, are the measures best able to show a real change after treatment.

So the technology is now good enough to track whether someone’s walking has actually changed after an intervention, rather than relying on impression. What it has not yet done is demonstrate that using it changes what we decide or how patients end up.

If one foot is warmer than the other at the same spot, that is a recognised early warning of damage in a foot with nerve damage: inflammation heats the skin before an ulcer can be seen. Insoles that take this reading at home twice a day and send it off for review are now being tested properly, including a 300-person trial in people with severe nerve damage from diabetes. In that trial, a difference of more than 1.5°C between the same spot on each foot, lasting over 32 hours, prompts action.

The concept is sound and the pilot data encouraging. Definitive outcome results are what the field is waiting for.

Changed

• Continuous, real-world data has replaced the snapshot. We can now see what a foot does across six weeks rather than what it does in a ten-minute consultation
• Feedback loops work. Where devices tell patients something they cannot otherwise know, how much load, how much pressure, behaviour changes measurably
• Cost and accessibility have fallen far enough for clinic use rather than research-only use

Not changed

• Most published work still only shows that a device measures accurately, not that it leaves people better off. Those are two different things
• Studies are still small, and several of the key ones involved the companies making the devices
• Approval to sell a wellness gadget is not the same as proof that it works as medical treatment
• Measuring how far the foot tilts inwards or outwards, which matters most in deformity, is still the least reliable

• Use your watch for trends, not absolutes. Week-on-week change in your own activity is the informative signal
• Bring the data. A graph of daily step counts over three months is genuinely useful in a consultation, and better evidence than “I think I’m doing more”
• Don’t let a step target override symptoms. Chasing 10,000 steps through a painful tendon is a good way to make a tendinopathy worse. Load should be guided by response, not by a round number
• If you have diabetes and nerve damage in your feet, ask your diabetes team about pressure-sensing insoles. This is the application with the best evidence and the highest stakes
• If you have been told to partially weight-bear, ask how you are supposed to judge it. Practising on bathroom scales is imperfect but better than guessing, and the evidence suggests most people overload without realising

Technology is changing what can be measured about the foot and ankle. It has not yet changed the fundamentals: a careful history, examination and the right imaging remain what determine a diagnosis and a plan.

Mr Matthew Welck is a Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital, Stanmore, and Honorary Associate Clinical Professor at UCL. His research interests include three-dimensional and weight-bearing assessment of foot and ankle deformity and outcome measurement, and his research and publications record includes over 50 peer-reviewed papers. He sees patients across North and Central London.

This article is provided for general information and patient education only. It does not replace personalised medical advice. Always consult a qualified specialist for diagnosis and treatment.