A concerned mother is warning against the dangers of trampolines after her three year-old suffered a broken bone after visiting a trampoline park. Kait Ellen took to Facebook to warn other parents that children under age six that use trampolines are more susceptible to broken bones because their bones are fragile and still developing. Ellen’s son Colton broke his femur, which is the largest and strongest bone in the human body. Emergency rooms saw thousands of injuries in children from using trampolines in 2014, and the American Academy of Orthopaedic Surgeons advises that children under six should not use one to stay safe.

Read more: Mom of Injured Toddler Warns Parents About Trampoline Danger