Postoperative pain following total knee arthroplasty (TKA) is often difficult to manage, particularly with the increasing use of outpatient surgery where patients recover at home. This study aims to evaluate whether wearing a knee extension brace for the first 72 hours after surgery can reduce pain and improve recovery.

This pilot randomized controlled trial will compare two groups of patients undergoing primary unilateral TKA: one group will wear an extension brace continuously for 72 hours after surgery, while the control group will follow standard care with early mobilization. Participants will be followed for up to 12 months.

The primary objective of this pilot study is to assess the feasibility of conducting a larger trial, including recruitment rates, adherence to the intervention, follow-up completion, safety, and acceptability. Clinical outcomes will also be explored, including pain at 2 and 6 weeks after surgery (measured using a visual analog scale), knee function, range of motion, opioid consumption, complications, healthcare use, and quality of life.

The study hypothesizes that short-term immobilization of the knee in full extension will reduce postoperative pain and may improve early recovery outcomes. Findings from this pilot study will inform the design of a larger definitive trial and may contribute to improving postoperative care and pain management after knee replacement surgery.

Postoperative pain following total knee arthroplasty (TKA) remains a significant clinical challenge, particularly in the context of increasing use of outpatient surgical pathways. Optimizing early postoperative pain management is essential to improve recovery, reduce unplanned healthcare utilization, and support enhanced recovery after surgery (ERAS) principles.

This study aims to evaluate the effect of short-term postoperative immobilization using a knee extension brace (Zimmer-type) worn continuously for 72 hours following primary unilateral TKA on postoperative pain at 2 and 6 weeks, measured using the Visual Analog Scale (VAS). The study hypothesizes that maintaining the knee in full extension during the immediate postoperative period will reduce pain and improve early recovery outcomes.

Study Design

This study is a pilot randomized controlled trial with a 1:1 allocation ratio and a single-blind design, in which outcome assessors are blinded to group allocation. The study is conducted at a single center (CHUS, Estrie, Canada).

Participants undergoing primary unilateral TKA will be randomized into one of two groups:

Intervention group: immobilization of the operated knee in full extension using a Zimmer-type brace for 72 hours postoperatively, followed by standard physiotherapy care.

Control group (standard of care): no restriction in movement, with early supervised mobilization according to usual physiotherapy practice.

The study adopts a pragmatic approach, allowing variability in physiotherapy delivery to reflect real-world clinical practice and enhance external validity. Timing and frequency of physiotherapy sessions will be recorded.

Study Objectives

The primary objective of this pilot study is to assess feasibility, including:

Recruitment rate and participant flow (inclusion, exclusion, refusal) Follow-up completion rate (target ≥80%) Intervention adherence (target ≥80% compliance in the intervention group) Safety, based on postoperative complication rates (including deep vein thrombosis, wound complications, and joint stiffness) Acceptability of the intervention and study procedures among patients and healthcare providers Estimation of variance in VAS pain scores to inform sample size calculation for a future definitive trial

The clinical primary outcome is postoperative pain at 2 and 6 weeks measured using the VAS, reported as mean differences between groups with 95% confidence intervals.

Secondary clinical outcomes include:

Knee range of motion (ROM) Postoperative opioid consumption Postoperative complications Emergency department visits and hospital readmissions Health-related quality of life (EQ-5D-5L) Knee function (Knee Society Score [KSS] and Functional KSS) Blood loss (hemoglobin levels) Postoperative inflammation (C-reactive protein) Study Population

The study population includes adults aged 18 years and older undergoing primary unilateral TKA for knee osteoarthritis at CHUS.

Key exclusion criteria include:

Known thrombophilia or bleeding disorders History of thromboembolic events Contraindications to brace use (e.g., material allergy) Revision or constrained knee prostheses Use of continuous postoperative nerve block infusion Sample Size

The pilot study aims to recruit 106 participants (53 per group) over an 18-month period, representing approximately 15% of the estimated sample size required for a definitive trial. Data from this pilot will be used to refine sample size calculations.

Recruitment and Procedures

Eligible patients will be identified during orthopedic consultations and approached for participation. After informed consent, baseline data (demographics, clinical characteristics, and preoperative measures) will be collected.

Randomization will occur on the day of surgery. The intervention will be applied by the orthopedic surgeon.

Follow-up assessments will occur at:

2-5 days postoperatively 2 weeks 6 weeks 3 months 12 months

Data collected include patient-reported outcomes, clinical assessments, laboratory values, and healthcare utilization. Participants in the intervention group will record brace wear time and opioid consumption using daily logs.

Data Collection and Outcomes

Pain will be assessed using the Visual Analog Scale (VAS). Additional outcomes include ROM measured with a goniometer, validated questionnaires (KSS, FKSS, EQ-5D-5L), laboratory markers (hemoglobin and C-reactive protein), and postoperative complications.

Opioid consumption and brace adherence will be self-reported using patient diaries. Healthcare utilization (emergency visits and readmissions) will be collected retrospectively.

Data Analysis

Feasibility outcomes will be analyzed descriptively using an intention-to-treat approach. Recruitment, adherence, and completion rates will be reported with 95% confidence intervals.

Comparisons between groups for exploratory clinical outcomes will be conducted using appropriate statistical tests depending on data distribution. This pilot study is not powered for definitive efficacy conclusions but will provide estimates to guide a larger trial.

Inclusion Criteria:

• Person undergoing primary unilateral TKA for knee osteoarthritis at CHUS

Exclusion Criteria:

• Known thrombophilia or bleeding disorders
• History of thromboembolic events
• Contraindications to brace use (e.g., material allergy)
• Revision or constrained knee prostheses
• Use of continuous postoperative nerve block infusion

De-identified individual participant data (IPD) will be made available upon reasonable request to the corresponding investigator.

Data will be available beginning 6 months following publication of the primary results and ending 5 years after publication.

Access will be granted to researchers who provide a methodologically sound proposal. Requests will be reviewed by the study team, and data sharing will require a data use agreement.