is a deficit
in turning the ankle
upward, known as dorsiflexion. Conditions leading to foot drop may be neurologic, muscular or anatomic in origin, often with significant overlap.
Foot drop is characterized by steppage gait
. When the person with foot drop walks, the foot slaps down onto the floor. To accommodate the toe drop, the patient may use a characteristic tip-toe walk, raising the thigh excessively, as if walking upstairs, while letting the toe drop. This serves to raise the foot high enough to prevent the toe from dragging, and prevents the slapping. Other gaits such as a wide outward leg swing (to avoid lifting the thigh excessively or to turn corners in the opposite direction of the affected limb) may also indicate foot drop.
Patients with painful disorders of sensation (dysesthesia) of the soles of the feet may have a similar gait, but do not have foot drop. Because of the extreme pain evoked by even the slightest pressure on the feet, the patient walks as if walking barefoot on hot sand.
Initial diagnosis often is made during routine physical examination: a person with foot drop will have difficulty "heel walking".
The causes of foot-drop, as for all causes of neurological lesions should be approached using a localization focussed approach before etiologies are considered.
Treated systematically, possible lesion sites causing foot drop include (going from peripheral to central)
- Muscle disease
- Peroneal nerve (common i.e. frequent)
- Sciatic nerve
- Lumbosacral plexus
- L5 nerve root (common, especially in association with pain in back radiating down leg)
- Spinal cord (rarely causes isolated foot drop)
- Brain (uncommon, but often overlooked)
- Genetic (as in Hereditary Neuropathy with liability to Pressure Palsies)
If the L5 nerve root is involved the most common cause is a herniated disc.
Other causes of foot drop are for an example: diabetes, trauma and Motor Neuron Disease (MND)
The underlying disorder must be treated. For example, if a spinal disc herniation
in the low back is impinging on the nerve that goes to the leg and causing symptoms of foot drop, then the herniated disc should be treated.
Ankles can be stabilized by lightweight orthoses, available in molded plastics as well as softer materials that use elastic properties to prevent foot drop. Additionally, shoes can be fit with springs to prevent foot drop while walking. Regular exercise is usually prescribed.
The latest treatments include stimulation of the peroneal nerve that lifts the foot when you step. Many stroke and multiple sclerosis patients with foot drop have had success with it.