CompletedObservational

Physical activity patterns after knee arthroplasty: recovery of physical activity after knee replacement surgery

Having a knee replacement is a big step, and many people wonder how quickly they will get back on their feet. The PAPrKA study aims to answer this by looking at real-world activity data people have already collected on their everyday gadgets, such as Fitbits, Apple Watches, Oura Rings, or iPhones. Researchers at the University of Manchester are inviting adults who had a partial or total knee replacement for osteoarthritis between 2017 and 2023. To take part, you need to have recorded your activity for at least six months before surgery and twelve months after. Joining is simple and done entirely online. You will sign an electronic consent form, complete a short survey, and securely share your device data. No hospital visits or tests are required. The results will help doctors give clearer, more realistic recovery advice to future patients.

At a glance

Status

Completed

Sponsor

University of Manchester

Enrolment target

1,000

Start

17 Nov 2025

Estimated completion

31 Jul 2026

Musculoskeletal

What is this study about?

Knee replacement surgery is a common and effective operation for severe knee osteoarthritis. Even so, many people preparing for surgery ask the same questions: How soon will I be active again? Will I walk more than before? How long does healing take? At the moment, doctors do not have detailed day-to-day data to answer these questions accurately for every individual.

The PAPrKA study aims to solve this by looking at everyday movement patterns. Instead of asking patients to remember how active they were months ago, researchers are using actual data already recorded by everyday devices, including Apple Watches, iPhones, Fitbits, and Oura Rings. By comparing activity levels from six months before surgery to a full year after, the team can map out typical recovery journeys.

Researchers will also link this activity data to information held by the National Joint Registry, an official UK database that tracks joint replacement surgeries. Combining these details will show whether factors like age, gender, or the type of knee replacement affect how quickly someone gets moving again.

Ultimately, this research could make a real difference for future patients. By showing true, real-life recovery patterns, it will help people set realistic personal goals and help surgeons give clearer advice on what to expect after knee surgery.

Key takeaways

The PAPrKA study investigates real-world physical activity recovery after knee replacement surgery.
It uses past step and activity data already recorded on smartwatches, fitness trackers, or iPhones.
Taking part involves an online survey and secure data sharing, with no hospital visits needed.
Open to UK adults who had knee replacement for osteoarthritis between 2017 and 2023.
The findings will help future patients and doctors understand what typical recovery looks like.

Who may be eligible?

You may be able to join this study if you had a total or partial knee replacement for osteoarthritis between 1 January 2017 and 31 December 2023. You must have been at least 18 years old when you had the surgery, and the operation must have taken place in England, Wales, Northern Ireland, or Guernsey.

Because the study looks at historical activity, you must have tracked your movement using an Apple iPhone, Apple Watch, Fitbit, or Oura Ring for at least six months before your surgery and for at least twelve months after it.

You cannot take part if you had your knee replacement for reasons other than osteoarthritis, or if you had your surgery outside the listed regions or dates. You will also need to understand English (or have someone to help you) and be able to provide consent online.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I had a partial or total knee replacement between 1 January 2017 and 31 December 2023.
My surgery was done to treat knee osteoarthritis.
I had my operation in England, Wales, Northern Ireland, or Guernsey.
I was 18 years of age or older at the time of my operation.
I tracked my daily activity on an Apple Watch, iPhone, Fitbit, or Oura Ring for at least 6 months before and 12 months after surgery.
I can complete an online consent form and questionnaire in English.

Answer every question to see your result.

What does participation involve?

Taking part in this study is entirely online, so you will not need to travel, attend hospital appointments, or take any medicine. First, you will read an information sheet and give consent online. Next, you will fill out a short survey about your background and knee surgery. Finally, you will follow simple instructions to securely connect your fitness tracker or smartphone account so the research team can download your past activity data. Once these steps are done, your active role is complete. The researchers will then link your movement data with records from the National Joint Registry. The whole study runs until December 2026.

Potential risks and benefits

Taking part will not change your medical treatment or improve your knee directly, but you will be contributing to important research that can help future patients know what to expect after surgery. The study involves no physical tests or procedures, so there is no risk of physical harm. The main consideration is data privacy, but the researchers follow strict UK data protection laws and security standards to keep your information safe and confidential. Taking part is completely voluntary, and you are free to change your mind and withdraw at any time without affecting your normal healthcare.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

No participating NHS sites. Recruiting via Be Part of Research Volunteer Service and other methods
City only
-, England

Common questions

Will I need to visit a hospital or clinic?

No. The entire study takes place online from your home. You do not need to attend any appointments or undergo any medical tests.

Does taking part affect my current NHS care?

Not at all. This study only looks at data from surgery you have already had. Your routine healthcare and relationship with your doctors will remain exactly the same.

Which devices can I use for this study?

You must have tracked your daily movement using an Apple iPhone, Apple Watch, Fitbit, or Oura Ring for six months before your operation and twelve months after.

Is my personal information secure?

Yes. The study team uses secure digital systems that follow strict NHS and university privacy standards. Your data will be kept confidential and stored safely.

Can I leave the study if I change my mind?

Yes. You can withdraw from the study at any time without giving a reason, and it will not affect your medical care in any way.

How to find out more

Louise Cook

paprka@manchester.ac.uk +44 0161 306 2719 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.