Foot drop is difficulty lifting the front part of the foot, causing toes to drag on the ground while walking. This impaired ability to raise the foot, known as dorsiflexion, can affect one or both feet. It is a symptom, not a disease, indicating an underlying issue with the nerves, muscles, or anatomy involved in foot movement.
Understanding Foot Drop and Contractures
Foot drop manifests as weakness or paralysis in the dorsiflexor muscles. When these muscles are compromised, individuals often adopt a “steppage gait,” raising their thigh higher than usual to avoid tripping over their dragging toes. This can cause the foot to slap down with each step.
A contracture, in contrast, involves the shortening and tightening of soft tissues like muscles, tendons, or skin, which restricts the normal range of motion at a joint. While foot drop is an impairment of movement ability, a contracture represents a structural change in the tissues that physically limits movement.
Foot drop itself is not a contracture. However, if foot drop is left unaddressed, the foot may remain in a downward (plantarflexed) position for extended periods, leading to specific types of contractures. An equinus contracture, for instance, can develop due to muscle imbalance and shortening of the Achilles tendon, making it difficult to bring the foot back to a neutral position.
Why Foot Drop Occurs
Foot drop can arise from problems affecting the nervous system or muscles. A common cause is injury to the peroneal nerve, a branch of the sciatic nerve controlling foot lifting muscles. This nerve runs close to the surface of the skin near the knee and can be compressed or damaged by activities like prolonged leg crossing, squatting, or kneeling.
Traumatic injuries, such as fractures of the ankle or fibula, or complications from hip or knee replacement surgeries, can damage the peroneal nerve. Furthermore, a “pinched nerve” in the spine, specifically a nerve root injury in the lumbar region (L5 radiculopathy), can impair nerve signals to the foot muscles, causing foot drop.
Disorders affecting the brain and spinal cord are another cause. Conditions like stroke, multiple sclerosis (MS), cerebral palsy, and amyotrophic lateral sclerosis (ALS) can disrupt the neurological pathways that control foot movement. Muscle disorders, including muscular dystrophy, which cause progressive weakness, also contribute to the development of foot drop.
Identifying the Cause of Foot Drop
Diagnosing foot drop begins with a neurological examination. During this assessment, a healthcare provider will evaluate muscle strength, reflexes, and sensation in the affected leg and foot. This helps to pinpoint the pattern of weakness or numbness.
Imaging studies visualize the nerves, muscles, and surrounding structures. Magnetic Resonance Imaging (MRI) provides detailed images of soft tissues and bones, identifying nerve compression from disc herniations, tumors, or other lesions. Ultrasound checks for cysts or swelling on the nerve.
Electrodiagnostic studies, including nerve conduction studies (NCS) and electromyography (EMG), are performed. NCS measures electrical signals travel along nerves, identifying nerve damage or demyelination. EMG involves inserting needles into muscles to record their electrical activity, revealing nerve or muscle disorders and determining the extent of injury.
Treatment Approaches for Foot Drop
Treatment for foot drop varies by cause and severity. Conservative management is often the initial approach, especially for less severe cases or when the cause is expected to resolve. Physical therapy strengthens leg muscles and maintains range of motion in the ankle and knee.
Ankle-foot orthoses (AFOs) or splints support the foot in a normal position, preventing dragging and assisting with walking. These devices prevent the development of contractures by keeping the foot from prolonged plantarflexion. Pain management techniques address any associated discomfort.
When conservative treatments are insufficient, or for specific underlying causes, surgical interventions are considered. Nerve decompression surgery can relieve pressure on a compressed nerve, while nerve transfers involve rerouting a healthy nerve to reinnervate the affected muscles. Tendon transfers are another surgical option, where a working tendon from one part of the foot or leg is moved to help restore the ability to lift the foot.