Foot Drop

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Foot drop is the inability to dorsiflex the foot due to weakness or paralysis of the muscles that lift the foot, leading to an abnormal gait pattern.

Aetiology

Foot drop results from damage to the peroneal nerve, motor neurons, or central nervous system pathways.

1. Peripheral Causes (Most Common):

  • Common peroneal nerve palsy: compression or injury at the fibular head.
  • Lumbosacral radiculopathy (L4/L5): nerve root compression due to herniated disc or spinal stenosis.
  • Peripheral neuropathy: seen in diabetes mellitus, Guillain-Barré syndrome.
  • Trauma: fractures of the fibula or knee dislocation affecting the peroneal nerve.

2. Central Causes:

  • Stroke: upper motor neuron lesion leading to unilateral weakness.
  • Multiple sclerosis: demyelinating lesions affecting motor pathways.
  • Cerebral palsy: congenital motor neuron dysfunction.

Pathophysiology

  • The common peroneal nerve (branch of the sciatic nerve) innervates the tibialis anterior, extensor hallucis longus, and extensor digitorum longus.
  • Damage to this nerve disrupts dorsiflexion, causing foot drop.
  • Patients develop a high stepping gait to compensate for the inability to clear the foot during walking.

Risk factors

  • Prolonged leg crossing or kneeling (nerve compression).
  • Diabetes mellitus (peripheral neuropathy).
  • Spinal pathology (herniated disc, spinal stenosis).
  • Neuromuscular disorders (motor neurone disease, muscular dystrophy).
  • Previous lower limb fractures or surgery.

Signs and symptoms

Patients with foot drop exhibit characteristic motor dysfunction.

Motor Symptoms:

  • Weakness of dorsiflexion: difficulty lifting the foot.
  • Weakness of toe extension: difficulty extending the toes.
  • Steppage gait: high stepping gait to compensate for foot drag.

Sensory Symptoms (if peroneal nerve involvement):

  • Numbness or tingling over the dorsum of the foot.
  • Loss of sensation between the first and second toes (deep peroneal nerve involvement).

Investigations

  • Clinical examination: assess dorsiflexion strength and gait pattern.
  • Electromyography (EMG): identifies nerve conduction abnormalities.
  • Nerve conduction studies (NCS): determines site and severity of nerve damage.
  • MRI lumbar spine: if radiculopathy (L4/L5 compression) is suspected.
  • Ultrasound of peroneal nerve: evaluates nerve compression at the fibular head.
  • Blood tests: HbA1c for diabetes, vitamin B12 levels for neuropathy.

Management

1. Conservative Management:

  • Physiotherapy: strengthening exercises for foot dorsiflexion.
  • Foot drop splint (ankle-foot orthosis, AFO): maintains foot position and improves walking.
  • Avoiding pressure on the peroneal nerve: avoid prolonged leg crossing or tight footwear.

2. Pharmacological Management:

  • Neuropathic pain relief: amitriptyline, gabapentin, or pregabalin if nerve pain is present.
  • Treatment of underlying cause: managing diabetes, vitamin B12 deficiency, or inflammatory conditions.

3. Surgical Intervention:

  • Decompression surgery: if nerve entrapment (e.g., at the fibular head) is identified.
  • Nerve grafting: considered in traumatic nerve damage with poor recovery.
  • Tendon transfer: for permanent foot drop, transferring functioning tendons to restore dorsiflexion.

4. Long-Term Monitoring and Rehabilitation:

  • Regular physiotherapy to maintain muscle strength and mobility.
  • Close monitoring for progressive neurological deterioration.
NeurologymypanotesFoot Drop