This study is a parallel-group superiority randomised controlled trial. Alongside this, a health-economic study and a process-evaluation study will be conducted. Participating patients will be allocated to either exercise and patient education or usual care at a 1:1 ratio. The primary outcome is change in self-reported pain measured with Copenhagen Hip and Groin Outcome Score (HAGOS) from baseline to 6-month follow-up.~The effectiveness of exercise and patient education compared with usual care will be reported in the primary trial paper, including the primary outcome and the following secondary outcomes: HAGOS symptoms, HAGOS function in daily living (ADL), HAGOS function in sport and recreation (sport/recreation), HAGOS participation in physical activity (participation), HAGOS quality of life (QOL), the impact of hip disease with the Short Version of the International Hip Outcome Tool (iHOT-12), lower limb reach length (anterior, posteromedial, posterolateral), single-leg hip for distance (SLHD) test and hip muscle strength (flexion, extension and abduction).~The primary aim of this effectiveness trial is to investigate if patients with hip dysplasia randomised to exercise and patient education have a different mean change in self-reported pain measured by the Copenhagen Hip and Groin Outcome Score (HAGOS) compared with those randomised to usual care over a six-month follow-up period.~The primary hypothesis: Patients randomised to exercise and patient education will have a between-group mean change score on the HAGOS pain that is at least 10 points higher than those randomised to usual care over a 6-month follow-up period.~The secondary aims are to compare mean changes between the two groups on the other HAGOS subscales over a 6-month follow-up period. Similar comparisons will be made on self-reported mean changes in the Short Version of the International Hip Outcome Tool (iHOT-12) and mean changes in performance, balance and hip muscle strength.~A full trial protocol will be published and made publicly available. All primary and secondary outcomes will be analysed with the intention-to-treat principle. Between-group differences from baseline to 3-month and 6-month follow-up of continuous outcomes will be estimated using repeated measurement analysis in a mixed-effects model, including patient as a random effect, with a fixed factor for group and time and the corresponding interaction (Group × Time), adjusted for baseline values. Between-group differences of continuous outcomes from baseline to 6-month follow-up will be analysed with an unpaired t-test, where between-group differences of categorical data from baseline to 6-month follow-up will be analysed with a binominal regression model using risk difference as a measure of association. In this paper, all collected outcomes will be listed, and it will be described that the below listed will be reported in other papers (i.e. health-economic study and process-evaluation study) and secondary papers.~In the health-economic study, the investigators will investigate the cost-utility and cost-effectiveness of exercise and patient education compared with usual care over 12 months. Outcomes for this paper will be measured at baseline, 3-, 6-, 9- and 12-month follow-up. Incremental cost-effectiveness ratios (ICER) will be calculated by dividing the difference in costs by the difference in effects (quality-adjusted life years and HAGOS pain). The uncertainty around the ICER and 95% confidence intervals (CIs) surrounding the cost differences will be estimated with 95% bootstrapped CIs based on non-parametric bootstrapping and will be graphically presented on cost-effectiveness planes and cost-effectiveness acceptability curves.~In the process-evaluation study, the investigators will explore the functioning of the intervention by evaluating the implementation, mechanisms of change and the contribution of contextual factors over 6 months.~Implementation includes the implementation process, fidelity, dose and reach. The implementation process will evaluate the structures and resources through which delivery is achieved. Fidelity aspects will evaluate the extent to deliver each component as planned and registered during the intervention period using self-report questionnaires. The dose will evaluate how much intervention is delivered and registered during the intervention period using routine monitoring forms, and reach will be evaluated as patterns in uptake and adherence by baseline patient characteristics registered before and during the intervention period. Mechanisms of change include interactions between the intervention, the intervention providers and the patients. Interactions will be evaluated through four semi-structured focus group interviews with the intervention providers and the expert team (study coordinator, Kristian Thorborg and Julie S. Jacobsen) and quantitative data on reasons for not receiving surgery. Contextual factors will include events, personal understandings and interactions and their possible influence on the implementation. Contextual factors will be evaluated through one-to-one semi-structured interviews during and after the intervention period with 15-20 patients in the intervention group. Findings from quantitative and quantitative analyses will be merged, interpreted and reported jointly.~The below listed will be reported in secondary papers with a clear reference to the primary trial paper and trial registration, and it will hold secondary analyses from a randomised controlled trial in the title.~By using subgroup stratification, we will explore if muscle-tendon pain and pain sensitisation modify between-group changes of the primary and secondary outcomes over 6 months. Furthermore, we plan to conduct an instrumental variable analysis on primary and secondary outcomes in an attempt to investigate the efficacy of the intervention. These analyses will be reported in secondary papers with clear reference to the primary trial paper.~In addition, the investigators plan to evaluate the psychometric properties of HAGOS and iHOT-12 in patients with hip dysplasia, and finally, the investigators plan to describe if hip osteoarthritis progresses over 5 and 10 years using the Tönnis osteoarthritis classification.
This effectiveness trial will investigate if patients with hip dysplasia randomised to exercise and patient education have a different mean change in self-reported pain measured by the Copenhagen Hip and Groin Outcome Score (HAGOS) compared with those randomised to usual care over a six-month follow-up period.~Participating patients will be allocated to either exercise and patient education or usual care. Alongside this, a health-economic study and a process-evaluation study will be conducted.