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CompletedNCT05900791Updated May 15, 2025

Persistent Pain After Knee Replacement

An observational study in Persistent Postsurgical Pain, Arthritis Knee and Neuropathic Pain, sponsored by University Hospital Bispebjerg and Frederiksberg. Completed at 1 site in Denmark. Open to participants aged 18 Years to 99 Years. Per ClinicalTrials.gov, last updated 2025-05-15.

Sponsored by University Hospital Bispebjerg and Frederiksberg · Observational

Study type
Observational
Model
Cohort
Time perspective
Cross-sectional
Enrollment
3,710
Ages
18 Years to 99 Years
Sex
All
01

Study summary

This study is a nationwide cross-sectional survey on pain and satisfaction after knee arthroplasty (KA). Please find the full protocol uploaded at ClinicalTrials.gov

The goal of this observational study is to study pain and satisfaction in patients operated with knee arthroplasty. The main question it aims to answer are:

  • What is the incidence of persistent postsurgical pain in unselected knee arthroplasty patients
  • What is the level of satisfaction in unselected knee arthroplasty patients?

Participants will be asked to answer a 22-item questionnaire.

Read the detailed description

The study is registered at the Capitol region of Denmark's regional research listing (Pactius) with identifier P-2023-4, approved 4 January 2023. The resulting paper will be reported according to the CROSS checklist for standardised reporting of survey studies. Wherever needed, a trained linguist translated questions from English to Danish and vice versa. The Danish and an English version of the questionnaire will be available in the final publication.

  • Study design: This study is a nationwide cross-sectional survey.
  • Patient involvement: A panel of KA patients helped develop the questionnaire, i.e., testing and selecting the questions.
  • Questionnaire: The questionnaire is composed of 22 questions (please see the uploaded protocol), however patients answering "No" to question 3 skips questions 4-17 concerning pain in the operated knee. Only question 3, 4, 20, and 21 are mandatory as to avoid non-respondents. The full questionnaire translated to English can be found in the supplementary material in the protocol. Contact information for the first author (JL) is supplied in the contact letter in case the patients have difficulties with filling in the questionnaire, have questions, or believe they have been selected mistakenly. Similar or identical questions to those in a survey published in 2006 to increase the ability to compare results (i.e., questions 3-5, 8, 10 and 18)
  • Sample characteristics: Eligible patients are all adult (18 years or older) patients operated with primary total or medial unicompartmental KA for osteoarthritis between August 1 and November 30, 2023. Legally incompetent citizens, i.e., persons with a legal guardian, will not be asked to participate. For total KA, patients are identified from the Danish National Patient Register through the Danish Health Data Authority (SKS-code DM17 [knee osteoarthritis] + KNGB20, KNGB30 or KNGB40 [primary total knee arthroplasty]). For medial unicompartmental KA, patients are identified from the Danish National Patient Register through the Danish Health Data Authority (SKS-code DM17 [knee osteoarthritis] + KNGB01 or KNGB11 [primary medial unicompartmental knee arthroplasty]).
  • Sample size calculation: The sample size calculation is based on the primary outcome in total KA patients. With an estimated 16% incidence of the primary outcome3 and a 70% response rate, 3172 patients are needed to yield a 95% confidence interval of 3 percentage points (14.6-17.6). In our opinion, this level of certainty is appropriate because differences less than this, may be hard to interpret by clinicians and patients. Sampling patients that were operated during 4 months outside holiday season should yield approximately this number of identified patients
  • Ethical considerations: The local institutional review board approved the study, and the Danish Health Data Authority will provide contact information for potential respondents. Telephone numbers for non-respondents are found by searching the CPR number in the electronic patient files, but without accessing the patients' health data. According to Danish legislation, approval from the national ethics committee is neither required nor possible to obtain for survey studies.
02

Conditions studied

  • Persistent Postsurgical Pain
  • Arthritis Knee
  • Neuropathic Pain
  • Opioid Use
03

In context

Neuralgia

1,287 studies on the registry are indexed under Neuralgia; 256 are open to participants now.

This study's enrollment of 3,710 is above the median of 100 across 260 observational studies indexed under Neuralgia.

Browse Neuralgia studies →

Lead sponsor

University Hospital Bispebjerg and Frederiksberg is the lead sponsor of 68 studies on the registry; 19 are open to participants now.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years to 99 Years
Sexes eligible
All
Accepts healthy volunteers
No
Sampling method
Non-probability sample

Study population

For total KA, patients are identified from the Danish National Patient Register through the Danish Health Data Authority (SKS-code DM17 [knee osteoarthritis] + KNGB20, KNGB30 or KNGB40 [primary total knee arthroplasty]).

For medial unicompartmental KA, patients are identified from the Danish National Patient Register through the Danish Health Data Authority (SKS-code DM17 [knee osteoarthritis] + KNGB01 or KNGB11 [primary medial unicompartmental knee arthroplasty]).

Inclusion criteria

  • Patients operated with primary knee arthroplasty for osteoarthritis 12-15 months before survey distribution

Exclusion criteria

Exclusion Criteria:

  • Legally incompetent citizens, i.e., persons with a legal guardian, will not be asked to participate.
05

Study design

Observational model
Cohort
Time perspective
Cross-sectional
Enrollment
3,710 participants (actual)
Patient registry
No

Interventions

  • ProcedurePrimary knee arthroplasty

    All patients surveyed have undergone primary knee arthroplasty approximately 1 year prior to survey distribution

    Also known as: Primary knee replacement

06

What researchers measure

Primary outcomes

  1. Moderate/Severe persistent postsurgical pain

    The main outcome is the number of patients with moderate or severe persistent postsurgical pain in the operated knee, defined as patients with a numerical rating scale (NRS) score higher than 3. The NRS score was dichotomised for the primary outcome because this is more intuitively understood by patients and clinicians. This outcome will be reported as percentage of all patients with 95% confidence interval, which is calculated with assumed binomial distribution as p ± 1.96 √( (p (1 - p) ) / n)

    Time frame: 11-15 months postsurgically

Secondary outcomes

  1. How satisfied are you with the outcome of your knee replacement surgery? Very satisfied, Satisfied, Neither satisfied nor dissatisfied, Dissatisfied, Very dissatisfied

    Reported as n (%) for each response option. The 1st question assesses overall satisfaction with surgery and have been translated directly from the questionnaire used by the Swedish Arthroplasty Register.

    Time frame: 11-15 months postsurgically

  2. Knowing what your knee replacement surgery did for you, if you could go back in time, would you still have undergone this surgery? Yes, No, Uncertain

    Reported as n (%) for each response option.

    Time frame: 11-15 months postsurgically

  3. Pain frequency: Do you still have pain in the operated knee? Yes, constantly; Yes, daily; Yes, a few times a week; Yes, more rarely; No

    Reported as n (%) for each response option.

    Time frame: 11-15 months postsurgically

  4. Numerical Rating Scale (NRS) pain: Please rate your pain in the operated knee by indicating the number that best describes your pain on average during the last week. 0 means 'No pain' and '10' means 'Pain as bad as you can imagine'.

    Reported as median (interquartile range \[IQR\]) and number of respondents

    Time frame: 11-15 months postsurgically

  5. Pain domain of the likert-scale version 3.1 of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

    The five questions in the WOMAC pain domain can be scored 0-4, where 0 is 'none' and 4 is 'extreme'. This results in an overall score of 0-20, which will be reported as median (IQR). Moreover, each response option of the individual questions are reported as n (%).

    Time frame: 11-15 months postsurgically

  6. Pain interference: In total, how much does the pain in the operated knee bother you in your everyday life? Not at all, A little, Some, Much, Very Much

    Reported as n (%) for each response option

    Time frame: 11-15 months postsurgically

  7. Douleur Neuropathique 4 questions (DN4) interview

    Each of the seven questions in the DN4 interview can be scored 0/1 (no/yes), which results in an overall score of 0-7. A score ≥3 constitutes 'possible' neuropathic pain. Both the median (IQR) DN4 interview score and number of patients (% of all patients) with possible neuropathic pain will be reported.

    Time frame: 11-15 months postsurgically

  8. Other pain: Do you have chronic pain, other than from your operated knee? Yes; No. [If yes] -> Please describe your pain condition

    Pain conditions will be categorised independently by two authors and reported as n (%).

    Time frame: 11-15 months postsurgically

  9. Analgesic use: Do you take analgesic medication(s) daily or almost daily? Yes; due to pain in the operated knee; Yes, due to other pain; No. [If yes] -> Which medication(s)?:

    Reported as n (%).

    Time frame: 11-15 months postsurgically

  10. Height (cm)

    Time frame: 11-15 months postsurgically

  11. Weight (kg)

    Time frame: 11-15 months postsurgically

07

Study locations

1 site
  • Bispebjerg University Hospital
    Copenhagen, 2200, Denmark
08

References and documents

Study documents

  • Protocol and statistical analysis plan · Jun 2, 2023

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: No — The full dataset will be stored at the Danish national archive (www.rigsarkivet.dk) if possible

09

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on May 15, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
10

Registry details

Key details

Study ID
NCT05900791
Lead sponsor
University Hospital Bispebjerg and Frederiksberg
Responsible party
Jens Laigaard (Principal investigator, University Hospital Bispebjerg and Frederiksberg) — Principal investigator
First posted
Jun 13, 2023
Start date
Nov 1, 2023
Primary completion
Dec 31, 2023
Completion
Dec 31, 2023
Last update
May 15, 2025

Study contacts

Søren Overgaard, MD, PhD, Professor
study director · Department of orthopedic surgery, Bispebjerg University Hospital, Denmark

Oversight

Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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