Feasibility and Preliminary Clinical Evaluation of a State-Based Load Tolerance and Rule-Based Individualized Rehabilitation Pathway in Youth Athletes With Current or Previous Lower-Extremity Apophyseal Pain

This study evaluates a structured rehabilitation pathway for youth athletes with current or previous lower-extremity apophyseal pain, including Osgood-Schlatter-related knee pain and Sever-related heel pain. The rehabilitation pathway combines a state-based early load-management framework with a rule-based individualized exercise program and education for safe return to sport.

The rehabilitation pathway is built around the Load Tolerance and Participation (LTP) Module. This module is used to classify each participant's current clinical state before rehabilitation progression. Classification is based on symptom irritability, participation restriction, clinical complexity, and recent load history. The purpose of this classification is to guide early decisions about activity modification, pain monitoring, exercise starting level, and progression or temporary regression of loading.

All participants in this study receive the same overall rehabilitation framework. However, the content is individualized using predefined decision rules rather than clinician preference alone. Each participant receives: (1) a mandatory core module focused on pain/load tolerance, education, and activity modification; (2) one main deficit-targeted exercise module, selected according to baseline clinical findings; and (3) an optional additional module only when a second deficit is clearly present and clinically relevant. Deficit-targeted modules may address range of motion/flexibility, strength, or motor control.

This study includes three pre-specified rehabilitation entry pathways. The first pathway includes participants who enter rehabilitation after completing the separate 2-week sham-controlled photobiomodulation trial (NCT07446517). The second pathway includes participants with active apophyseal pain who are not enrolled in that trial and enter rehabilitation directly after baseline assessment. The third pathway includes participants with a history of Osgood-Schlatter-related or Sever-related symptoms, or those with low-irritability/residual presentations, who enter rehabilitation directly in a lower-intensity or simplified pathway. These pathways are defined at study entry and will be used for pre-specified exploratory subgroup analyses. They are not intended to support causal comparisons of treatment effectiveness between groups.

The rehabilitation phase includes in-person physiotherapy visits and a home exercise program. During follow-up, participants and families are instructed in pain monitoring, symptom-guided activity modification, weekly tracking of symptoms and sport exposure, and safe stepwise return to sport. Rehabilitation progression is guided by predefined pain-monitoring rules and trend monitoring across time, rather than by fixed timelines alone.

This rehabilitation study is methodologically linked to the separately registered pilot sham-controlled photobiomodulation trial in youth athletes with apophyseal pain. Participants who complete that trial may enter this rehabilitation study through the post-trial pathway. However, the present study is focused on the rehabilitation pathway itself and is registered separately because the rehabilitation intervention, timing of entry, and clinical questions differ from those of the photobiomodulation trial.