Adolescents are susceptible to patellar sleeve fractures. We present an interesting case of a patellar sleeve fracture in an 11-year-old child with lateral slip of the retinacular sleeve. Clinical assessment was difficult; however, an MRI scan confirmed the diagnosis. Surgical repair was undertaken, and the retinacular sleeve was repaired along with repair of the patellar tendon. The patient recovered well after surgery and underwent physiotherapy. A patellar sleeve fracture should always be suspected in patients less than 16 years of age, particularly in those with indirect acute trauma to the knee. Prompt surgical repair is important to achieve full functional recovery.