Drop foot and foot drop are interchangeable terms that describe an abnormal neuromuscular (nerve and muscle) disorder that affects the patient's ability to raise their foot at the ankle. Drop foot is further characterized by an inability to point the toes toward the body (dorsiflexion) or move the foot at the ankle inward or outward. Pain, weakness, and numbness may accompany loss of function.
Drop Foot/Foot Drop: A Symptom
Drop foot is not a disease but a symptom of an underlying problem. Depending on the cause, drop foot may be temporary or permanent. Often drop foot is caused by injury to the peroneal nerve deep within the lumbar and sacral spine. The peroneal nerve is a division of the sciatic nerve. The peroneal nerve runs along the outside of the lower leg (below the knee) and branches off into each ankle, foot, and first two toes. It innervates or transmits signals to muscle groups responsible for ankle, foot, and toe movement and sensation.
Peroneal Nerve: Causes of Injury
The peroneal nerve is susceptible to different types of injury. Some of these include nerve compression from lumbar disc herniation (eg, L4, L5, S1), trauma to the sciatic nerve, spondylolisthesis, spinal stenosis, spinal cord injury, bone fractures (leg, vertebrae), stroke, tumor, diabetes, lacerations, gunshot wounds, or crush-type injuries. Drop foot is found in some patients with Amyotrophic Lateral Sclerosis (ALS), Multiple Sclerosis (MS), and Parkinson's Disease. Sometimes the peroneal nerve becomes injured when stretched during hip or knee replacement surgery.
Proper Diagnosis of Underlying Cause
The diagnostic process includes a comprehensive assessment of the patient's symptoms, past and current medical histories, physical and neurological examinations, imaging studies such as MRI (magnetic resonance imaging), and EMG (electromyogram). The spine specialist must determine the cause of drop foot before formulating a treatment plan.
Drop Foot (Foot Drop) Treatment
The type of treatment is dependent on the underlying cause of drop foot. Some patients may be fitted with an Ankle Foot Orthosis (AFO), brace, or splint that fits into the shoe to stabilize the ankle/foot. Gait training may be incorporated into the patient's physical therapy treatment plan.
Surgery may be an option to correct or alleviate the underlying problem causing drop foot. For example, if drop foot is caused by nerve compression from a lumbar herniated disc, then a spinal surgical procedure called discectomy (disc removal) may be required to relieve or 'decompress' the nerve.
In some cases, drop foot is a complex problem. Determining the underlying cause of drop foot is one of the physician's first considerations.