Foot drop syndrome is caused by weakness that occurs in specific muscles of the ankle and the foot. The affected muscles participate in the downward and upward movement of the ankle and the foot. The specific muscles include the anterior tibialis, extensor hallucis longus, and the extensor digitorum longus. The normal function of these muscles is to allow the toes to swing up from the ground during the beginning of a stride and to control the movement of the foot following the planting of the heel towards the end of the stride. Abnormal muscle function makes it difficult to prevent the toes from clearing the ground during the stride.
Some people with foot drop walk with a very exaggerated swinging hip motion to help prevent the toes from catching on the ground. Another symptom of foot drop, which occurs as the foot is planted, is an uncontrolled slapping of the foot on the ground.
There are three general causes of the muscle weakness. Damage to nerves can affect the transmission of impulses that help control muscle movement and function. Motor neuron diseases such as Amyotrophic Lateral Sclerosis (ALS) or post-polio syndrome, tumors in the brain or spinal cord, or diseases of the nerve roots of the lumbar spine are all neurological conditions that may produce foot drop. Second, the muscles themselves may be damaged. Third, there can be some skeletal or other anatomical abnormality that affects the movement of the ankle or foot. A combination of these factors can also be involved, as is the case with the drop foot malady known as Charcot foot.
