Study design and setting
This study consists of the development and evaluation of the Sorting non-trauMatIc adoLescent knEe (SMILE) tool for non-traumatic knee pain in adolescents. The study was conducted at the Center for General Practice at Aalborg University between February 2019 – February 2020 and inspired by requests from our reference group of general practitioners (GPs).
Step One: Development of the SMILE tool
Systematic search
The systematic literature search was conducted in Medline (via PubMed). The search strategy was developed using medical subject headings and text words related to knee, pain, and diagnosis. The search strategy is available in Additional file 1. No language restriction was applied to the search. We included papers published between 1950 and until 1st of March 2019. We also conducted a hand search including the reference lists of included studies and the authors’ personal files to make sure that all relevant material has been captured.
Eligibility criteria for including articles (both narrative and systematic) were articles describing any type of diagnostic, clinical assessment, or physical examination concerning non-traumatic knee pain. Articles on any age group were eligible, providing they described assessment/diagnosis of knee pain conditions seen in adolescents (e.g. studies on diagnosis of patellofemoral pain and ITBS in adults were eligible). Articles describing treatment only were excluded. Endnote version X9.1.1 was used to include or exclude articles.
Potentially eligible articles were independently screened by title/abstract and full text by one author (CG). Data were independently extracted and evaluated by discussion by two authors (CG and MES) into data extraction forms based on the Cochrane data extraction forms. We extracted data on study characteristics, prevalence of conditions, risk factors, clinical history and test for each diagnosis in the articles. Any discrepancies between forms were evaluated through discussion in the group.
Development process of the SMILE tool
Information from the review was then synthesised in a summary for each condition (see Additional file 2 and methods). This was supplemented by Brukner and Khan’s Clinical Sports Medicine 5TH edition, and input from international experts in sports medicine (published authors with more than five years of clinical experience), and GP’s with a special interest in sports medicine.
This information was then transformed into the SMILE tool. Table 1 shows an overview of the boxes included in the SMILE tool. Feedback on the content, layout, and text/frames used for the first version was sought from international experts and from medical doctors in a pilot test. The process from the first draft of the tool to the final version is shown in Additional file 2.
Table 1. Contents of SMILE tool
Overview of boxes in the SMILE tool
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Non-traumatic onset of knee pain
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The first question is related to the onset of knee pain e.g. if the onset is non-traumatic with symptom getting worse and with no traumatic event at that point of time
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Symptoms and pain localisation
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Pain during loading activities
Pain outside the knee joint
Pain anterior on the knee à where on front of the knee (tuberosity of the tibia, lower pole of the patella or around/behind the patella)
Pain lateral on the knee or at the distal thigh
Pain on the medial side of the knee
Pain on the posterior side of the knee
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Pictures of pain localisation
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Each diagnosis is presented with a picture of the precise pain localisation
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Tentative diagnosis – information boxes of each diagnosis
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Pain localisation on palpation
Epidemiology with sex differentials and age range
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Differential diagnoses
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Consist of the most important diagnoses that may not be missed in the clinic. Their symptoms and clinical characteristics
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Step two: Validation of the SMILE tool
After an initial pilot evaluation of the SMILE tool with one medical doctor and one medical student, we modified the layout based on feedback, and subsequently assessed and iterated the SMILE tool on two different test days. The content of the different test days and how we optimised and evaluated the SMILE tool after the test days is described in figure1.
Recruitment of participants with knee pain
Inclusion criteria were adolescents (both sexes) aged 10-18 years, with a non-traumatic onset of knee pain. If adolescents had a traumatic event leading up to their onset of knee pain or had undergone surgery on the knee, they were excluded.
We recruited participants through flyers, videos on social media (Facebook and Instagram) and from local sports clubs.
Recruitment of medical doctors and medical students
The assessors were medical doctors or medical students recruited from the Center for General Practice and through our professional network. The medical students were required to be in their final year of medical educated needed to become a doctor in Denmark. We included medical students because the target end-users are inexperienced medical doctors without specific training/education in sports medicine or musculoskeletal disorders. We aimed that the SMILE tool would be feasible for medical doctors, independent of clinical experience with non-traumatic knee complaints in adolescents. Special care was taken to include assessors with varying interests in sports medicine. We included nine medical doctors and medical students (two younger medical doctors and seven medical students) as assessors in our study. Separate assessors were used at each session to ensure they were not familiar with the tool before assessments.
We recruited two specialists to serve as gold standards. The first (JLO) participated in the pilot test and test day 1, while the second (MSR) participated in the test day 2. Gold standard 1 is a specialist in rehumatology and sports medicine with 15 years of clinical and scientific experience in diagnosing and treating adolescents with knee pain15. Gold standard 2 is a physiotherapist and an experienced clinical researcher with a specific clinical and research interest in adolescent knee pain16
Examination of the SMILE tool through three different test days and data collection
Assessors received no training on the SMILE tool or its content, aside from a 1-minute introduction. Assessors were interviewed regarding their perception of using the SMILE tool, and any potential areas of improvement. At each consultation assessors documented baseline characteristics (name, age, months with knee pain), diagnosis without and with the SMILE tool, and time spent on the consultation (see Figure 1). Participants completed self-report questionnaires on knee pain duration, sports participation, and the Knee injury and Osteoarthritis Outcome Score (KOOS child) which has previously been used in adolescent populations with overuse related injuries17. Figure 1 gives an overview of the different test days and the data collection.
Statistical analysis
Baseline characteristics for adolescents were calculated using descriptive statistics. To test the validity of the SMILE tool we calculated the percentage agreement without and with the SMILE tool between the diagnoses given by the assessors and the gold standards diagnoses. We tested the inter-rater reliability of the SMILE tool using Fleiss kappa statistics and McNemar’s test to determine differences in proportion correct diagnoses with and without the SMILE tool. Descriptive statistics were performed using Microsoft excel version 16.34. Fleiss kappa and McNemar’s test were calculated in R version 3.5.3.