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

The goal of this clinical trial is to learn if a 12-week individualized rehabilitation program is feasible and helpful for children and adolescents with lower-extremity apophyseal pain, including Osgood-Schlatter-related knee pain and Sever-related heel pain. It will also learn about how well participants follow the program, whether the program can be delivered as planned, and whether pain, function, and sports participation improve during rehabilitation. The main questions it aims to answer are: 1. Can this rehabilitation program be delivered with good attendance, good home-exercise adherence, and complete follow-up data? 2. Do pain, function, and sports participation improve during the rehabilitation period? 3. Which baseline clinical, functional, ultrasound, maturity, or biomarker features may help explain who responds better to rehabilitation? All participants will receive the same overall rehabilitation framework. The program includes education, pain and load monitoring, an activity-ladder approach, symptom-guided exercise progression, motor-control training, basic strength exercises, and gradual return to running, jumping, landing, and sport-specific activities. Exercises are individualized according to symptoms, current activity level, movement quality, treatment tolerance, and clinical judgement. Participants will: 1. Attend baseline and follow-up physiotherapy assessments. 2. Receive an individualized rehabilitation plan with education, pain and load monitoring, and home exercises. 3. Complete home exercises and keep a short symptom and activity log. 4. Attend in-person physiotherapy review visits during the rehabilitation period. 5. Answer questionnaires about pain, function, perceived change, and sports participation during follow-up.