Physical activity pre- and post-total knee replacement, using NHS and consumer health and fitness tracker data

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This is one of two research projects leveraging digital technology to combat knee impairments such as osteoarthritis. The University of Manchester is the home institution for this project. To view the Melbourne-based partner project, click here.

The uptake of consumer technology has been significant in the last 10 years. Mobile devices collect digital traces from our everyday lives, for example tracking patterns of activity. Such data may be successfully reused for health research. One disease area where mobility is notably impacted by symptoms is arthritis, making this an interesting use case to understand how we might make use of retrospectively collected consumer data for health insights. Total knee replacements (TKRs) are a common surgical procedure for knee osteoarthritis.

Prior to surgery, clinicians and patients need to make shared informed decisions about the likely benefits and potential harms of surgery. Benefits commonly cited include improvements in pain and discomfort and improvement in mobility. Improvements in pain are supported by strong evidence, however, changes in mobility and activity levels are less clear. Understanding the patterns of physical activity pre-and post-op have historically been limited to physical activity questionnaires. Some studies are starting to use more objective measures including accelerometry – although this typically requires the provision of devices and prospective data collection. To date, the numbers of such studies are limited, outcome measures vary, and assessment is at fixed intervals such as 6- or 12-months post-op.

In the population of 80k UK total knee replacement patients per year, a subset will have been tracking their physical activity data via consumer devices (Fitbit, Google Fit, Strava etc). This provides a major opportunity to learn about changes in activity from real-world data. It is important to understand, though, whether this subset is representative of the whole population of interest, and how the findings can (or cannot) be extrapolated. We also need to know what aspects of activity are of interest to stakeholders, especially patients, so that the analysis can be usefully translated into meaningful information to guide shared informed decision making in the future.

Project goals

The goals of this project are:

  1. To conduct a systematic literature review to summarise what is known about physical activity pre-and-post-TKR;
  2. To conduct a qualitative study in pre-operative and post-operative TKR patients to explore physical activity behaviours and determine what digital health information should be used to summarise patterns of activity pre-and-post-TKR;
  3. In partnership with Fitbit and Janeiro Digital, to identify patients who have undergone TKR, collect consent, and link their Fitbit data with their NHS data;
  4. Analyse the linked data to:
    1. Understand the representativeness of Fitbit-owning TKR patients;
    2. Generate descriptive statistics of activity levels pre-and-post-TKR;
    3. Examine patterns of activity in those with good and bad outcomes.

Supervision team

The University of Manchester: Professor William Dixon

The University of Melbourne: Doctor Stephanie Filbay, Professor Kim Bennell and Doctor Mark Merolli

*Click on the researcher's name above to learn more about their publication and grant successes.

Who we are looking for

We are seeking a PhD candidate with the following skills:

  • Demonstrated experience in a related field (e.g. physiotherapy, medicine, psychology, health sciences, epidemiology).
  • Demonstrated ability to work independently and as part of a team.
  • Demonstrated time and project management skills.
  • Demonstrated ability to write research reports or other publications to a publishable standard (even if not published to date).
  • Excellent written and oral communication skills.
  • Demonstrated organisational skills, time management and ability to work to priorities.
  • Demonstrated problem-solving abilities.

Further details

The PhD candidate will benefit from the combined expertise of the project supervisors, and the embedding into two research environments.

This PhD project will be based at the University of Melbourne with a minimum 12-month stay at the University of Manchester. The candidate will be enrolled in the PhD program at the Centre for Health, Exercise and Sports Medicine, Melbourne School of Health Sciences (CHESM) at the University of Melbourne. CHESM is a multi-disciplinary team world-renowned for its clinical and translational research in knee osteoarthritis. Candidates will have access to internal and external grant funding and will benefit from CHESM’s strong early-career researcher program including formal mentoring, exchange visits, seed funding and leadership training. Candidates will receive further mentorship from international collaborators with expertise in physical activity interventions, digital health and behaviour change theory.

The candidate will be simultaneously enrolled in the PhD program at the Centre for Epidemiology Versus Arthritis, Division of Musculoskeletal and Dermatological Science, School of Biological Science at the University of Manchester, and whilst in Manchester, benefit from The Centre for Epidemiology Versus Arthritis’ expertise in mobile health study design, conduct, data analysis and interpretation of results. They will learn from a wide range of parallel mobile health studies being conducted in the department, as well as from historical studies and collective experience.

The candidate will attend the annual Manchester Digital Epidemiology Summer School and learn the fundamentals of clinical epidemiology and a series of more advanced methods through the regular departmental meetings and in-house training programs. The Centre for Epidemiology Versus Arthritis has ongoing industry collaborations with Google and Fitbit, providing insights into academic-industry partnerships. The PhD project proposal has been designed to allow the candidate to travel to Manchester after baseline collection of mobile health data, to receive specific training in data analytics related to the Fitbit device.

To apply for this joint PhD opportunity, and to view the entry requirements, visit How to apply.

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