Background <p>Osteosarcoma occurs most commonly during adolescence, a period of active skeletal growth. Beyond concerns regarding survival, patients and their families often worry that surgery, perioperative chemotherapy, and the physiological stress of treatment may adversely affect growth. Therefore, the purpose of this study was to evaluate growth patterns in the contralateral limb following treatment for high-grade osteosarcoma.</p> Methods <p>Consecutive patients 14 years of age or younger treated for high-grade osteosarcoma of the distal femur or proximal tibia between 2012 and 2020, with a minimum follow-up of 5&#xa0;years and contralateral limb MRI available, were retrospectively reviewed. Serial lower-extremity MRI was used to measure assess longitudinal and transverse skeletal growth. Growth trajectories were analyzed using linear mixed-effects models. Age- and sex-matched percentile curves were used to assess deviations from expected growth.</p> Results <p>Twenty patients (8 boys, 12 girls; mean age 11.7 ± 2.0 years) were analyzed. Continued contralateral femoral and tibial growth was observed in all patients until physeal closure, without premature growth arrest. Mean annual growth rates were 0.64 ± 0.47&#xa0;cm/year and 0.41 ± 0.14&#xa0;cm/year, respectively. Transverse skeletal growth remained proportionate. Nine of twenty patients (45%) demonstrated downward crossing of age- and sex-matched growth percentile bands during skeletal maturation.</p> Conclusions <p>Pediatric osteosarcoma patients treated with surgery and systemic chemotherapy demonstrated continued growth of the contralateral lower limb without premature physeal closure or disproportionate transverse remodeling. However, downward shifts in growth percentile trajectories were observed, and their clinical significance warrants further investigation.</p> <p><i>Level of Evidence</i> III, Retrospective cohort study.</p>