The Efficacy of a Smart Insole In Osteoarthritis/Total Knee Arthroplasty Patients.

The Efficacy of a Smart Insole In Osteoarthritis/Total Knee Arthroplasty Patients.


The White Paper summarised in the article aims to assess the effectiveness of a smart insole in the triage and rehabilitation of knee osteoarthritis (KOA) and knee arthroplasty (KA) patients.

A smart insole has the potential to be a key improvement to KOA patients’ quality of life (QoL) via rehabilitation and surgical prioritisation. The literature strongly advocates that smart insoles that monitor plantar pressure, gait, and activity levels can help healthcare professionals (HCPs) triage and rehabilitate KOA and KA patients.

Path Insight.

The Walk With Path team has been working on developing Path Insight, a smart insole that fits into everyday enclosed shoes aiming to collect data and give insights using Artificial Intelligence (AI) into a person's function in a useful format for patient education and to support clinical decision making. The insole collects data, such as plantar pressure, temperature and gait analysis, through sensors within the insole. The insole is characterised as smart, as it is connected to a smartphone app for the user and a digital downstream dashboard for healthcare professionals.

What is Knee Osteoarthritis (KOA)?

Knee osteoarthritis (KOA) is the progressive loss and damage of cartilage covering the bones in the knee joint, most common in the elderly. KOA symptoms often progress, becoming more severe, frequent, and debilitating, although the rate of this deterioration varies from person to person. Common symptoms include knee pain with a gradual onset that worsens with activity, knee stiffness, swelling, and pain after sitting/resting for extended periods of time. Interestingly, only 15–81% of patients with radiographic findings of KOA are symptomatic.

KOA is the most common type of arthritis diagnosed, and its prevalence will continue to increase as life expectancy and obesity rise. Research shows that in those over 70, up to 40% have KOA, with more women suffering from it than men.



The first-line treatment for all patients with symptomatic KOA is patient education and physical therapy. UK National Institute for Health and Care Excellence (NICE) guidelines recommend education, advice, information access, exercise and weight loss as core treatments for all osteoarthritis patients.


If an individual has symptomatic KOA in at least 2 of the 3 compartments of the knee and fails more conservative treatments, surgical procedures, such as knee arthroplasties (KAs), can be used. KAs, also known as knee replacements, are a method of reconstructing the knee joint by removing the damaged parts and replacing them with prostheses. Total knee arthroplasties (TKAs) are highly cost-effective, costing £5,623 per quality-adjusted life-year (QALY) gained per patient.

According to the United Kingdom NICE guidelines, for a patient to be eligible for a KA, there must be significant, prolonged symptoms with supporting clinical and radiological signs; however, beyond this, there is currently no specific threshold for KA patient prioritisation. Thus, in multiple countries including Canada and the UK, hospitals often use a 'first-come-first-served' rule or adopt their own policies on KA prioritisation.

The lack of effective patient prioritisation represents a major issue in several countries as KA delays correlate to greater pain, difficulty with functional tasks, less improvement post-surgery, and reduced quality of life. Although in 2004 the UK government set the goal to reduce waiting times from ‘18 months to 18 weeks’ and this was largely achieved for some time, this goal has not been reached for 5 years now.

Gait Changes in KOA.

Gait changes.

Patients with KOA demonstrate reduced gait parameters arising from joint stiffness or reduced muscle strength in the knees, and plantar pressure changes which contribute to foot pronation and pain. The inability to prioritise patients for KA can be solved by classifying KOA and other pathologies severity based on spatiotemporal gait analysis. The literature proposes for stride length and cadence to be used for the classification of KOA severity, where shorter stride length and lower cadence is associated with higher severity. A progressive decrease in cadence, walking speed, mean stride length, swing phase duration and single support phase, and increased stance phase duration and first double support phase correlates with increased KOA severity.

Plantar Pressure Changes.

It seems that individuals with KOA tend to have increased foot pronation. For example, some papers have found that plantar pressures in the midfoot and first metatarsophalangeal joint (MPJ) are higher in women with KOA than those without. Other papers have found that KA patients have much higher plantar pressure in the non-operated foot and the heel region of that foot compared to healthy individuals.

Gait Changes Following KA.

Gait parameters seem to improve following KAs. A recent systematic review concluded that TKAs consistently improve postural stability compared to the pre-surgery state. Gait speed, stride length, knee flexion/extension range, and maximal knee flexion all increase 1 year post-TKA compared to pre-TKA. Suh et al. found that gait speed and gait endurance are positively correlated to cadence and stride length while negatively correlated to timed up-and-go, stair-climbing test ascent, stair-climbing test descent, visual analogue scale, WOMAC pain indices, stiffness and function levels following TKAs. In other words, they found that the faster and more you can walk after KA, the greater your cadence, stride length, and functionality and the lower your pain and stiffness levels. However, some papers such as Heil et al. contradict this, showing no significant changes in postural sway or plantar pressure pre and post KA.

Despite improvements in gait parameters, post-KA compared to pre-KA, TKA patients still have worse balance compared to their healthy counterparts. Gait asymmetries in step length have been noted 15 weeks after surgery possibly due to the habit of using crutches in the early postoperative period.

Post-KA rehabilitation.

Current State of Post-KA Rehabilitation.

The goal of postoperative care for TKA patients is to restore the greatest possible mobility and muscle control to the knee. Adequate rehabilitation is important for achieving successful TKA outcomes. The exact rehabilitation programme differs from surgeon to surgeon. In-bed rehabilitation starts on day one of surgery. Full weight-bearing is also possible under the supervision of a therapist with a walker. More active rehabilitation exercises, such as straight leg raises, can start one day after surgery. Usually, patients have to show that they can safely walk with an assistive device on flat ground and stairs as well as show the ability to get into bed from sitting or standing positions and good pain control before being discharged from the hospital and going home or to a skilled nursing facility.

After leaving the hospital, patients get a postoperative visit at the two-week mark, where the wound is checked and surgical staples are removed. If not already begun, at this point outpatient physical therapy starts. It usually takes patients 4-6 weeks to improve to the point where they can resume driving and operate car gas pedals safely and rapidly. After 4-10 weeks they can get back to work, depending on what their job is. Patient follow-up is usually at 6 weeks, 3 months, and one year after surgery. Once strength, mobility, and balance are regained, patients can resume low-impact sporting activities although high-impact activities are discouraged.

Although post-surgery rehabilitation improves outcomes and can be more cost-effective than usual care for at least 9 out of 10 patients, >50% of patients fail to continue recommended aftercare following inpatient rehabilitation. NICE recommends the need for further research on long-term follow-up and monitoring after joint replacement surgery.

The Future of KA Rehabilitation.

There are now a few tech solutions targeting KA care. IDEEA(r), GaitSmart, SHIMMER3 IMU, and ActivPAL3(TM) are technologies that involve placing multiple sensors on the thighs, ankles, and feet or even taping sensors onto patients' skin. However, attaching multiple sensors can be complicated, bulky, and unseemly, making patients less likely to use them and limiting use to in-clinic.

While some of these solutions, such as GaitSmart, do provide personalised rehabilitation exercises for KA patients, they are too complicated for continuous monitoring and thus only function for in-clinic use. Providing only in-clinic monitoring makes such devices less likely to help physicians prioritise patients or motivate exercising devices that continuously patients and provides regular notification updates on their gait improvements such as actively(r) (gait analyzing belt) and mymobility (Apple Watch app). These, however, have lesser accuracy overall, and do not directly measure aspects such as pronation, an element directly linked to KOA pain, such as pronation. Currently, no pressure-sensing insoles for gait analysis pre- or post-KA are available on the market.


As research shows, there is a need for innovation and smart insoles such as Path Insight have a variety of potential applications in the KOA population. Not only can its ability to prioritise patients for KAs help decision making for healthcare professionals and tackle the massive KA backlog, via the use of both pain questionnaires and objective gait metrics, but it can also help reduce inequalities and biases in KA prioritisation. Furthermore, Path Insight’s app will be able to provide patients with standardised clinician-approved information on what to expect before, during, and after surgery. Finally, via monitoring patients’ gait metrics, Path Insight will be able to provide personalised physiotherapist-approved prehabilitation and rehabilitation exercises in order to get KOA and KA patients back on their feet.

To access the full White Paper and to read more about Path Insight and its ability to help professionals in the triage and rehabilitation of knee osteoarthritis and knee arthroplasty patients complete the form below.

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