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

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, Sever-related heel pain, and/or Sinding-Larsen-Johansson-related pain at the inferior pole of the patella, or has previous symptoms of these conditions 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, the inferior pole of the patella, 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