Foot drop, also known as drop foot, is a gait abnormality characterized by difficulty lifting the front part of the foot due to weakness or paralysis of the dorsiflexor muscles in the lower leg, leading to toe dragging or a slapping sound during walking.[1] This condition arises primarily from disruption in the nerve supply to these muscles, most commonly involving the peroneal (fibular) nerve, which controls foot and toe dorsiflexion.[2] It can affect one or both feet and significantly impacts mobility, often requiring compensatory high-stepping gaits to avoid tripping.[3]The most frequent cause of foot drop is peroneal nerve injury, which can result from compression at the fibular head—such as during prolonged leg crossing, knee trauma, or surgical procedures—or from systemic conditions like diabetes mellitus that predispose to neuropathy.[1] Other etiologies include lumbar radiculopathy (e.g., L4-L5 disc herniation), central nervous system disorders such as stroke, multiple sclerosis, or cerebral palsy, and muscular dystrophies affecting the anterior compartment muscles.[3] Less commonly, it may stem from Charcot-Marie-Tooth disease or trauma to the sciatic nerve.[2] Risk factors include habitual leg crossing, prolonged kneeling or squatting, and wearing a cast or brace on the leg.[1]Symptoms typically manifest as an inability to dorsiflex the foot, resulting in foot slapping, toe dragging, or circumduction during gait, alongside possible numbness or tingling in the lower leg if sensory nerves are involved. In severe cases, patients may experience frequent stumbling or falls, and unilateral foot drop can lead to an antalgic gait pattern.[4] Diagnosis often involves clinical examination, electromyography (EMG), nerve conduction studies, and imaging to identify the underlying pathology, while treatment varies by cause and may include ankle-foot orthoses, physical therapy, medications, or surgical interventions like nerve decompression or tendon transfers, as well as emerging functional electrical stimulation devices.[5][6] Early intervention is crucial to prevent muscle atrophy and contractures, potentially improving functional outcomes.[3]
Clinical Presentation
Signs and Symptoms
Foot drop is characterized by the inability to actively dorsiflex the foot or toes, particularly during the swing phase of gait, which results in the front of the foot dragging on the ground or producing a slapping sound upon heel strike.[1] This manifests as steppage gait, where patients compensate by excessively lifting the knee or hip to clear the foot, often leading to a high-stepping or exaggerated flexion pattern.[2] Patients commonly report frequent tripping, falls, difficulty ascending stairs, and a sensation of ankle instability due to impaired foot control.[7]The primary muscle weakness involves the tibialis anterior, responsible for ankle dorsiflexion, along with the extensor hallucis longus for great toe extension and the peroneus longus and brevis for foot eversion.[3] In cases of peroneal nerve involvement, sensory deficits may accompany motor symptoms, including numbness, tingling, or reduced sensation over the dorsum of the lower leg, foot, and toes.[8] These features contribute to broader gait abnormalities, such as circumduction or reduced walking efficiency.[2]The presentation may differ based on whether the underlying lesion is central (upper motor neuron) or peripheral (lower motor neuron). Central causes, such as stroke or multiple sclerosis, often feature spasticity, hyperreflexia, and a positive Babinski sign, potentially with associated upper limb or cognitive involvement. In contrast, peripheral causes like peroneal neuropathy typically present with flaccid weakness, hyporeflexia, and possible sensory loss or atrophy.[3]In chronic cases, affected muscles may exhibit visible atrophy, particularly in the anterior compartment of the leg, leading to a thinned appearance along the shin. Fasciculations, or involuntary muscle twitches, can also occur in the weakened muscles, signaling ongoing denervation.[3]
Gait Abnormalities
Foot drop primarily disrupts the swing phase of gait, where dorsiflexor weakness prevents adequate toe clearance, leading to toe drag or ground contact that compels compensatory movements to maintain forward progression.[3] In response, individuals often adopt a steppage gait, characterized by exaggerated hip and knee flexion to lift the foot higher and avoid scraping the toes, resulting in a high-stepping pattern that mimics a deliberate exaggeration of normal limb advancement.[9] Alternatively, circumduction gait may occur, involving lateral swinging of the leg in a circular arc during swing to circumscribe the dropped foot around obstacles, further altering the natural linear trajectory of the limb.[10]This reduced foot clearance during the swing phase—typically the minimum toe height of about 1-2 cm above ground in normal gait—significantly heightens the risk of tripping and falls, as even minor surface irregularities can cause the forefoot to catch.[11] If the underlying condition secondarily affects hip abductors, such as in L5 radiculopathy, a Trendelenburg gait emerges, marked by pelvic drop on the contralateral side during stance on the affected leg due to gluteus medius weakness, compounding instability.[12]These kinematic alterations significantly increase overall energy expenditure compared to normal walking, as the body recruits additional musculature for compensation, leading to rapid fatigue and reduced walking endurance over short distances.[13] Asymmetrical limb loading ensues, with greater reliance on the unaffected side for propulsion and balance, which imposes uneven stress on the knee and hip joints of both limbs, potentially accelerating degenerative changes over time.[14]In descriptive terms, the swing phase bears the brunt of impairment, with absent or diminished ankle dorsiflexion causing the foot to plantarflex and drag from mid-swing onward, while the stance phase experiences secondary effects like audible foot slap at initial contact and prolonged heel-off due to instability.