This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
People with ongoing pain after a knee replacement may benefit from personalised follow-up, research shows. A detailed assessment, and referral to the relevant specialist, reduced long-term pain. The approach was cost-effective, the study found.
Knee replacement surgery relieves pain and reduces disability for many people. But about 1 in 5 continue to have long-term pain afterwards. The cause of the pain – and the most appropriate treatment – can vary. Pain may be related to inflammation, a misplaced new joint, depression, or many other factors. There is no single treatment.
This study assessed a new care pathway, called STAR (Support and treatment after joint replacement). It is intended for people with pain 8 weeks after surgery, and aims to prevent the pain becoming long-term. People have a detailed assessment, and are then referred to an appropriate specialist. This could be to a physiotherapist for muscle strengthening exercises, for example, or to a surgeon for problems with the surgery. People receive up to 6 telephone calls over the next 12 months, to track their progress.
After a year, people offered the STAR care pathway reported less severe pain than people who had usual care. Care using the STAR pathway was more cost effective than usual care.
Further information on knee replacements is available on the NHS website.
UPDATE (08/03/2024): Follow-up at 4 years suggested some sustained benefit from the STAR intervention, though longer-term benefits were uncertain due to high numbers of participants dropping out of the trial. The intervention remained cost-effective.
What’s the issue?
Every year, more than 100,000 people in the UK have a total knee replacement, most often to treat osteoarthritis (painful and stiff joints). Surgery reduces pain and disability for most people, but around 1 in 5 have ongoing pain. Earlier work by this research team found that people may need encouragement to seek help.
Ongoing pain after knee replacement is complex and can be related to different factors. Factors known to be associated with ongoing pain include inflammation, infection, nerve damage, incorrect positioning of the replacement joint, and depression. People’s pain may be related to just 1 factor or a number of different factors. Interventions can target these factors, but it can be difficult for people to access the help they need.
The research team developed a personalised care pathway, called STAR. People are sent a questionnaire 8 weeks after their knee surgery, to identify early those who are still in pain. An allied health professional with training in orthopaedics (bones and joints) carries out a detailed assessment within 3 months of surgery. This may include pain questionnaires, X-rays, and blood tests for infection.
People are then referred for the most appropriate treatment. This could mean referral to an orthopaedic surgeon for pain associated with surgery or infection. Alternatively, the referral could be to a physiotherapist for muscle strengthening exercises, or to a GP for treatment of depression, anxiety, or nerve pain.
Over the next 12 months, people receive up to 6 telephone calls, where possible from the same allied health professional. The professional checks whether further referrals are needed.
Usual care for people not receiving the STAR pathway is 1 routine follow-up appointment roughly 8 weeks after surgery, and some clinicians provide a further assessment at 12 weeks. Usual care does not include routine assessment and follow-up by professionals specialising in pain.
Researchers wanted to see if the STAR pathway could make a lasting difference to pain and its impact on daily life. They also considered the costs of care.
What’s new?
The study took place in 8 NHS hospitals. People who had a knee replacement were sent a pain questionnaire 8 weeks after surgery. Those who described knee pain were invited to take part in the study (363 people). All received usual care but 2 in 3 people in the study had the STAR pathway in addition.
After 12 months, researchers asked people to report their knee pain on a scale of 0 (best) to 10 (worst).
They found that people in the STAR group had:
- less severe pain (3.1 with STAR compared to 3.7 with usual care alone)
- less interferences of pain in everyday life (3.5 with STAR compared to 4.1 with usual care alone).
The researchers looked at the costs of the care pathways. They considered costs to the patient, to the NHS and to social services, including hospital admissions, outpatient visits, and primary care. People on the STAR pathway had better recovery at lower cost, they found. On average, the STAR pathway cost £724 less per person than usual care. The difference in costs was mainly because people receiving usual care had more hospital admissions and took more unpaid leave from work.
Why is this important?
Treating long-term pain is expensive and difficult. A care pathway that allows prompt assessment of pain after a knee replacement, and referral to appropriate services, could improve its management. Addressing pain early is likely to reduce the risk of it becoming long-term.
The STAR pathway made a small but important difference to pain scores. The improvement in pain was slightly less than 1 point (the minimum to correspond to meaningful change). The researchers say that STAR is the first personalised intervention for managing long-term knee pain that provides value for money. It led to some improvements in pain, for lower costs.
The researchers interviewed people who had used the STAR pathway (reported separately). Many were unprepared for the severity of pain after knee replacement, and how long it takes to recover afterwards. People who received the care pathway said it was a welcome source of support. Follow-up by the same professional could create a caring atmosphere, and improve people’s overall wellbeing. The researchers say the STAR pathway gave people reassurance and confidence in their recovery.
The STAR pathway can be integrated into routine healthcare. It is safe and acceptable with most (96%) people attending the assessment. However, for many (29%) the assessment took place 4 months or more after surgery. This suggests there may be challenges to delivering the start of pathway within the intended 3 months.
What’s next?
The STAR pathway could be adapted as strategies for managing long-term pain develop. The research team plans to publish information on long-term (4-year) follow up of people who were involved in the study of the STAR pathway. They are also looking at implementation of the pathway. So far, it has been implemented as part of usual care at North Bristol NHS Trust.
In this study, 92% of the participants were White. This broadly reflects the people having total knee replacements in the UK. Further research could investigate the effectiveness of the pathway in a more diverse population.
Further research could also explore whether a similar pathway is effective in other healthcare areas.
You may be interested to read
This summary is based on: Wylde V, and others. The STAR care pathway for patients with pain at 3 months after total knee replacement: a multicentre, pragmatic, randomised, controlled trial. Lancet Rheumatology. 2022;4:3.
People’s experiences of the STAR care pathway: Moore, A, and others. Experiences of recovery and a new care pathway for people with pain after total knee replacement: qualitative research embedded in the STAR trial. BMC Musculoskeletal Disorders. 2022;23:451.
The cost-effectiveness analysis: Cole S, and others. Modelled cost-effectiveness analysis of the Support and Treatment After Replacement (STAR) care pathway for chronic pain after total knee replacement compared with usual care. Cost Effectiveness and Resource Allocation. 2024; 22(28).
A news release about the study written by the University of Bristol.
NIHR summary of work from the same project: Ongoing pain after knee replacement: people need support and encouragement to seek help.
Thanks to the STAR team for providing the video that accompanies this Alert.
Funding: This study was funded by an NIHR Programme Grant for Applied Research.
Conflicts of Interest: Several authors have received fees and funding from pharmaceutical companies, unrelated to this work.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
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