Changes in daily sedentary time, in adolescents with long-standing knee pain, during a management strategy including activity modification: An ancillary analysis of two clinical trials.

Objectives: The aim was to investigate changes in sedentary time during an activity modification strategy for sports-active adolescents with patellofemoral pain (PFP) and Osgood-Schlatter (OSD).

Design: Explorative ancillary analysis of two different prospective clinical trials with two different endpoint timelines.

Methods: 202 adolescents with either PFP or OSD were included. ActiGraph GT3X + objectively measured sedentary time before, during, and after adolescents were instructed to modify sports participation, requiring a minimum of 4 days with 10 h of wear time. Daily sedentary time was calculated from ≥10 min of consecutive bouts.

Results: 138 adolescents with PFP and 47 with OSD were eligible for inclusion. Adolescents with PFP had a non-significant increase of 14min/day change in sedentary time from baseline to during the activity modification. Adolescents with OSD had non-significant increases of 9min/day and 0min/day in sedentary time from baseline to immediately following the activity modification period and at the 12 weeks follow-up. There was variability in the individual adolescents' sedentary time during the intervention.

Conclusion: Activity modification in adolescents with PFP or OSD was associated with none, or only small systematic changes in sedentary time.