Individualized Rehabilitation for Osgood-Schlatter or Sever Pain in Youth Athletes

This study evaluates a 12-week individualized 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 study is designed as a prospective, single-arm interventional feasibility study with exploratory clinical-response and predictor analyses.

The rehabilitation pathway includes a standardized core framework delivered to all participants. The core components are education, pain and load monitoring, activity modification, symptom-guided progression, home-exercise prescription, basic strength exposure, motor-control training, and gradual return to sport-related loading. The main clinical emphasis is on improving load tolerance and movement quality during tasks relevant to youth sport, such as squatting, single-leg control, step or split-squat patterns, calf-loading tasks, landing, deceleration, running, and sport-specific activities.

The intervention is individualized pragmatically rather than by formal treatment allocation rules. Exercise selection and progression are adjusted according to each participant's symptoms, current participation level, irritability, movement quality, tolerance of the prescribed exercises, response after exercise, and clinical judgement. Baseline clinical and functional tests may include measures of range of motion, muscle strength, movement quality, ultrasound features, maturation, and biomarkers. These measures are used for participant characterization, safety monitoring, and exploratory predictor or moderator analyses. They are not used as a deterministic algorithm for assigning participants to separate treatment modules.

All participants receive the same overall rehabilitation pathway, but the exact exercise variants, starting level, loading dose, rate of progression, and temporary regressions may differ between participants. The rehabilitation program includes in-person physiotherapy visits at baseline and planned review time points, together with a home exercise program. Participants and families receive instructions on how to monitor pain, symptoms, and sport exposure, and how to respond if symptoms increase.

Progression is guided by symptom response and movement quality rather than by fixed timelines alone. Pain during exercise, symptom response after the session and the next day, perceived exertion, and visible movement quality are used to decide whether to maintain, progress, regress, or temporarily pause selected exercises or activity levels. Participants are instructed to report relevant symptom worsening, limping, swelling, new pain, or adverse events to the physiotherapy team.

The rehabilitation pathway uses an activity-ladder approach to guide return to participation. Sport participation and load exposure are monitored separately, because a participant may tolerate some parts of training while still being unable to tolerate higher-load tasks such as sprinting, jumping, landing, rapid deceleration, or match play. Return to sport is therefore progressed stepwise and individualized to symptom response.

The study also includes exploratory responder and predictor analyses. Baseline clinical features, symptom irritability, functional performance, ultrasound findings, maturity-related variables, and selected biomarkers may be examined as potential predictors or moderators of clinical response. These analyses are exploratory and are not intended to establish causal treatment effects between subgroups.

This rehabilitation study is methodologically linked to the separately registered pilot sham-controlled photobiomodulation trial in youth athletes with apophyseal pain (NCT07446517). Participants who complete that trial may enter this rehabilitation study through a post-trial pathway. Other eligible participants may enter the rehabilitation study directly after baseline assessment. The present study is registered separately because the rehabilitation intervention, timing of entry, and clinical questions differ from those of the photobiomodulation trial.

Inclusion criteria

• Aged 10 to 17 years
• Participates in organized sport and has at least 12 months of sport participation or training history
• Has current lower-extremity apophyseal pain consistent with Osgood-Schlatter-related knee pain and/or Sever-related heel pain, or has previous Osgood-Schlatter-related or Sever-related symptoms with a residual or low-irritability presentation relevant to rehabilitation
• Meets criteria for at least one pre-specified rehabilitation entry pathway:

post-trial rehabilitation entry after completion of the separate photobiomodulation trial, or direct-entry rehabilitation with active apophyseal symptoms, or direct-entry rehabilitation with previous Osgood-Schlatter-related or Sever-related symptoms and a low-irritability or residual presentation

For participants entering with active symptoms:

• pain is located at the tibial tubercle region and/or the calcaneal apophyseal/heel region
• pain is aggravated by activity, loading, or sport participation
• pain is reproducible on clinical examination or the clinical history is consistent with the target condition

Participant and parent/caregiver are willing to take part in the rehabilitation program, including in-person visits, home exercises, symptom/activity monitoring, and follow-up assessments.

A parent or legal guardian provides written informed consent, and the participant provides assent when applicable.

Exclusion criteria

• Current pain episode started after an acute traumatic injury that better explains the symptoms
• Clinical presentation suggests a condition other than the target rehabilitation condition, including a major alternative knee or heel diagnosis requiring different management
• Lower-limb surgery that would substantially affect rehabilitation planning, safety, or interpretation of outcomes
• Known serious musculoskeletal, neurological, rheumatological, inflammatory, autoimmune, metabolic, or other systemic disease that may affect safe participation or interpretation of outcomes
• Any medical or developmental condition that would prevent safe participation in exercise-based rehabilitation
• Current symptoms requiring urgent medical assessment or management outside the rehabilitation pathway
• Inability to understand study instructions or complete study procedures with parent/caregiver support
• Parent/caregiver or participant does not agree to participate or withdraws consent/assent