An upturned big toe may be caused by several reasons: 1. It may be caused by damage to the flexor tendon of the toe. This condition is often seen in patients with strenuous activities or plantar injuries that cause damage to the flexor tendons of the toes, which can lead to a disruption in the balance of flexion and extension forces of the toes. The constant pulling of the extensor tendon will cause the big toe to continue to buckle; 2. This condition may be caused by bony deformities around the toe, which are often due to old fractures of the toe or osteoarthritis in the first metatarsophalangeal joint or other diseases. Once this occurs, the patient will often have a persistent big toe upward, and there is no movement; 3, this condition may be due to peripheral nerve damage, such as patients with tibial nerve-related injuries, may lead to the entire plantar muscles, tendons weakness, and then lead to toe upward; 4, this condition may also be due to the sequelae of cerebral palsy and other diseases caused by 4. This condition may also be caused by diseases such as cerebral palsy.