Ptosis may be caused by injuries to the sciatic nerve, common peroneal nerve, sacral plexus nerve, cerebral nerve and so on. 1. Sciatic nerve injury: Sciatic nerve injury is caused by localized sharp instrument injury, pelvic fracture or hip dislocation, which results in foot drop and lower limb sensory disorder. 2. Common peroneal nerve injury: the common peroneal nerve is compressed or damaged on the lateral side of the knee joint, and the tibialis anterior muscle canals appear, which can lead to foot drop. 3. Sacral Plexus Nerve Injury: Due to the injury of sacral plexus nerve caused by fall from height, traffic accident or pelvic fracture, foot drop and difficulty in walking will occur. 4. Cerebral nerve injury: hemiplegia foot drop caused by cerebral infarction and cerebral hemorrhage. When foot drop occurs, it is necessary to go to the hospital for further examination to clarify the cause of the disease and then further treatment.