Development of the Core-Kids knee core set of outcome domains for studies of paediatric knee injuries

The incidence of paediatric anterior cruciate ligament (ACL) injury is increasing, especially in adolescent athletes and skeletal immaturity(1–3). Soft tissue knee injuries share the same increasing incidence, either in isolation or often, in association with each other due to the mechanism of injury(4). These include meniscal tears, patellofemoral pathologies such as dislocation, osteochondral dissecans and fractures(4,5). There is a sex disparity, with an eight-fold increase in ACL injuries disproportionately affecting female athletes more than males(6). Some examples illustrated in this review article summarise them to anatomical differences, biomechanics (congenital valgus knee angle) and hormonal factors, as well as the availability of training and prevention programmes(7). The prevalence of osteoarthritis increases with the passage of time since the index ACL injury and a three—to six-fold increase in the risk of the injured knee(1,8,9).

Outcomes for soft tissue knee injuries are among the NIHR James Lind Alliance's top 10 priorities amongst ages 12-17(1) through the Priority Setting Partnerships (PSP), as well as the number 1 priority for paediatric lower limb surgery: What are the best ways to measure the outcome following lower limb orthopaedic surgery in children?

Before trials can be delivered to compare treatments, we need to know which are the most relevant and valid outcomes to measure(10–13). Unfortunately, there is currently significant heterogeneity in the reporting of outcomes for paediatric knee injuries, which limits our ability to draw conclusions and compare study outcomes from trials(14).

We aim to develop a core outcome set for studies of paediatric knee injuries. This will involve agreeing on a minimum set of outcomes to be measured in all trials involving paediatric patients with soft tissue knee injuries. This will minimise reporting bias and allow trial outcomes to be pooled into more powerful analyses(10). These core outcome sets will focus on relevance to families, children and adolescents as well as clinicians treating these common injuries.


Mr Ignatius Liew (lead investigator)
MBChB FRCS (Tr & Orth), PG Cert
Specialist Registrar Trauma and Orthopaedic Surgery Eastern deanery
Cambridge University Hospital

Mr Ben Marson (lead supervisor)
PhD FRCS (Tr & Orth)
Consultant Paediatric Orthopaedic Surgeon
Nottingham University Hospital

Associate Professor Stephen McDonnell
Consultant Trauma and Orthopaedic Surgeon
Principal Investigator – ACL STARR: Anterior Cruciate Ligament Stratified Accelerated Repair or Reconstruction Single Blinded Randomised Control Trial for Patients with Proximal ACL Injuries Treatment with ACL Repair versus ACL Reconstruction

Further Study Information

Current Stage: Ongoing
Date: June 2024 - June 2026
Funding source(s): The Orthopaedic Trust (Gwen Fish Trust)

Health Area

Disease Category: Orthopaedics & trauma

Disease Name: Knee injuries

Target Population

Age Range: 5 - 16

Sex: Either

Nature of Intervention: Any

Stakeholders Involved

- Consumers (patients)
- Families
- Methodologists
- Researchers
- Service providers
- Service users

Study Type

- COS for clinical trials or clinical research
- COS for practice


- Consensus meeting
- Delphi process
- Interview
- Literature review
- Survey
- Systematic review


We will follow internationally recognised Core Outcome Measures in Effectiveness Trials (COMET) methodology(15), including:

Identification of candidate outcomes relevant to patients, surgeons and researchers
Prioritisation of outcomes
Agreement on the core outcome set

The study protocol will be registered on the COMET database, consistent with COS-STAR guidelines. The target population will range from age 5 to 16, where the highest incidence of paediatric knee injuries occurs. Ethical approval will be sought and registered with Birmingham Children’s Hospital.

Identification of candidate outcomes will be achieved by completing complementary projects:
1. A systematic review of previous trials (registered with PROSPERO) will identify the outcomes relevant to trialists.
2. A questionnaire will be circulated to the child knee network of surgeons and therapists to understand outcomes relevant to surgeons. The steering group will set the scope of the core outcome set.
3. A Technology of Participation meeting will be held with patients who have experienced these injuries, which will generate outcomes that are relevant to them.
4. An online Delphi consensus survey will be conducted, informing the final consensus meeting and developing the core outcome set for paediatric knee injuries

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