Aims: This study aims to report the medium term outcomes of circumferential periosteal release of the distal femur and distal tibia in treating paediatric leg length discrepancy (LLD). Materials and methods: A retrospective case series was performed on all patients undergoing circumferential periosteal release of the distal femur and/or tibia between 2006 and 2019. Data collected included demographics, surgical indications, post-operative leg lengths, and complications. Leg length discrepancy was calculated as actual values and percentages of the longest limb length. Final actual and percentage discrepancies were compared to initial discrepancies using a paired t-test. Patterns of discrepancy over time were analysed using linear mixed models. Results: Eighteen patients (11 males) were identified, who underwent 25 procedures. The mean age at first surgery was 5.8 (range, 2–13). The commonest indication was congenital limb deficiency (7 patients). Five patients underwent repeat periosteal release, and one patient had three releases. The mean follow-up was 63 months [standard deviation (SD), 33.9]. Fifteen patients had sufficient data for statistical analysis. The mean actual discrepancy decreased from 2.07 cm (SD, 1.07) to 1.12 cm (SD, 1.62), and the mean relative discrepancy from 4.3% (SD, 2.8) to 1.5% (SD, 2.4). Significant mean reductions were seen in both actual discrepancies [0.61 cm (95% CI: 0.05–1.16; p = 0.034)], and percentage discrepancy [2.10% (95% CI: 1.0–3.1, p = <0.001]). In five patients, the operated limb overgrew the contralateral limb. Patients whose operated limb overgrew still had a reduction in LLD, with a mean residual discrepancy less than 1 cm (mean 0.7 cm, 95% CI: From −0.9 to 2.4). Conclusion: Circumferential periosteal release produces a significant decrease in both actual and percentage LLD. We believe this procedure is best indicated in younger patients with congenital LLD in whom the discrepancy is predicted to increase as they age. Clinical significance: Circumferential periosteal release produces a significant decrease in LLD. This procedure can be used to manage symptoms during growth, particularly at the point where orthotic usage may become problematic, and to potentially reduce the magnitude of surgery needed at an older age.