BACKGROUND: Deleterious effects of lower limb immobilization in adults have been well described and suggest that altered muscle strength was not fully recoverable after rehabilitation. In this study, we hypothesized that the same significant differences in strength and power performances between the injured and noninjured leg are foreseeable 18 months after a lower limb fracture in teenagers, and between injured adolescents and healthy controls. METHODS: The effects of cast immobilization on the strength and power performance were evaluated 18 months after a lower limb fracture in 39 injured teenagers who were paired with healthy controls. Strength and power performance were assessed during a single-leg vertical jump test using a force platform. RESULTS: At 18 months, strength performance in injured teenagers was similar in both lower limbs. A significant difference was found between injured and noninjured legs for maximal muscular power measurement. However, the limb symmetry index was superior to 85% for maximal muscular power, which should be considered as normal. Limb asymmetries greater than 15% for muscular strength and power were more frequent in injured teenagers than in noninjured children and adolescents, but the difference was statistically significant only for the mean muscle power (P=0.0003). CONCLUSIONS: These findings show that the recovery of muscular strength and power is foreseeable after a lower limb fracture in the pediatric population, even if a greater percentage of injured teenagers was found to have limb asymmetries greater than 15% for mean muscular power 18 months after trauma compared with the healthy controls. LEVEL OF EVIDENCE: Level III, case-control study.