Statistical methods
SECONDARY
The statistical analyses were pre-planned prior to participant enrolment and published at clinicaltrials.gov (NCT01682980) before we revealed the group allocation. Descriptive baseline characteristics are presented for each group separately as number (n) and percentage (%), mean and standard deviations, or median and minimum-maximum (min-max) values depending on the type of the variable or its distribution. All outcomes were compared between each intervention group and the usual care group at the 4-month and 1-year follow-ups. To test the hypotheses for the primary outcome at 1 year, intention-to-treat mixed linear model with restricted maximum likelihood (REML) solution was applied using KOOS QoL data as the dependent variable. Because 7 participants withdrew their informed consents, we had to exclude these from our dataset. Consequently, a modified intention-to-treat analysis was conducted. The baseline score for KOOS QoL were included as covariate, the participant’s ID variable as a random effect, and intervention group, time, and group*time as fixed effect factors. The statistical analyses for secondary outcomes were conducted using the same approach as for the primary outcome. No adjustments for multiplicity were applied. Statistical Package for Social Sciences (IBM© SPSS© Statistics version 27) was used for the statistical analyses. Cost-effectiveness analyses will be reported in a separate paper.