The hazards of knee hyperextension mainly include knee joint damage, flat feet, abnormal gait and other hazards. 1. Knee joint injury: knee hyperextension leads to knee joint mechanical changes, the surrounding muscle imbalance, resulting in joint cartilage damage, meniscus, ligament and other structural damage is serious, serious cases can lead to knee joint degeneration and so on. In addition, joint damage easily leads to decreased joint stability, which is more likely to cause patients to have sports injuries, and will also make knee hyperextension become more serious. 2. Flat feet: knee hyperextension will make the muscles of the posterior group of the calf overstretched and tense, which will lead to plantar fascia tension, the patient’s plantar bones lose their support, and the arch of the foot collapses, resulting in the formation of flat feet. 3. Abnormal posture: knee hyperextension will lead to anterior pelvic tilt, resulting in leg rotation and increased burden on the patient’s lumbar spine. In addition, knee hyperextension also affects other joints such as the hip and ankle joints, and in severe cases, it can lead to abnormal walking posture. Patients with hyperextension of the knee should go to the relevant departments of regular hospitals as soon as possible and be treated by specialized physicians to avoid delays that may lead to adverse events.