Understanding Foot Drop: Causes, Diagnosis, and Treatments
What Is Foot Drop?
Foot drop refers to the inability to lift the front part of the foot, leading to difficulty with walking. This condition affects the swing phase of gait and causes the foot to drag on the ground unless compensatory movements, such as high knee lifting (steppage gait), are used​. Over time, abnormal gait mechanics can cause joint stress and even deformities like equinus contracture due to muscle imbalance and Achilles tendon shortening.
Although commonly seen in clinical practice, there is no specific diagnostic code for foot drop. It may be associated with different underlying conditions, and its prevalence remains unknown due to the lack of large-scale studies.
Causes of Foot Drop
Foot drop can arise from problems at any level along the neural pathway, from the brain to the peripheral nerves. Understanding the exact location of the lesion is key to determining appropriate treatment.
1. Central Causes
Lesions in the brain or spinal cord can lead to foot drop, although it is often part of a more widespread weakness. Common causes include:
- Stroke (especially in the anterior cerebral artery territory)
- Brain tumors
- Hemorrhages
- Inflammatory or ischemic lesions
Studies report that up to 14% of stroke survivors experience persistent foot drop, and in cases of spinal cord injury, the incidence can reach 76%​
2. Spinal Nerve Causes
Compression or herniation of lumbar discs, especially at the L5 nerve root, is a leading cause. Risk factors include:
- Polyneuropathy
- Large or calcified herniations
- Foraminal stenosis Ma et al. found that 23% of patients with L5 root involvement had clinical foot drop​
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3. Peripheral Causes
Injury to the peroneal nerve is the most frequent cause of isolated foot drop. It can result from:
- Compression at the fibular head (e.g., from sitting with crossed legs)
- Trauma
- Iatrogenic injury during surgeries
- Space-occupying lesions like ganglion cysts or tumors
Peroneal nerve injury accounts for 15% of all adult mononeuropathies​
Diagnosing Foot Drop
A thorough diagnostic workup is essential to identify the underlying cause and decide on the right course of treatment.
Clinical Examination
- Muscle strength testing, especially dorsiflexion
- Reflexes, including the tibialis posterior reflex
- Sensory mapping to identify nerve involvement
- Gait observation
Electrophysiology
- Nerve conduction studies and electromyography (EMG) help differentiate between radiculopathy and peripheral neuropathy.
- EMG can detect signs of axonal damage and reinnervation earlier than clinical observation​
Imaging
- MRI is used to assess central and spinal causes.
- Ultrasound and MR neurography help evaluate peripheral nerve lesions and cysts.
Treatment Options
Treatment depends on the cause, severity, and duration of foot drop. The goals are to restore function, improve mobility, and prevent complications.
1. Surgical Interventions
- Decompression or Neurolysis: If a compressive cause is identified early (preferably within 48 hours), decompression can offer excellent outcomes.
- Spinal Surgery: For disc herniations or spinal stenosis.
- Peripheral Nerve Repair: Requires short graft lengths (<6 cm) to avoid poor recovery.
Timely intervention is critical—nerve regeneration potential declines significantly after 3 months​
2. Tendon Transfers
For irreversible nerve damage, tendon transfer is a viable option:
- The posterior tibial tendon is rerouted through the interosseous membrane to replace dorsiflexion function.
- A stirrup configuration may also be used for better control. Although only 30% of the original strength is restored, most patients report improved mobility and satisfaction​
3. Functional Electrical Stimulation (FES)
FES applies small electrical pulses to stimulate nerves, encouraging foot lifting during walking:
- Comparable to ankle-foot orthoses (AFO) in improving walking speed​
- Especially beneficial when combined with rehabilitation.
- Reduces perceived exertion in patients with multiple sclerosis-related foot drop​
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FES is seen as cost-effective over time, with many patients continuing use for over a decade​.
4. Botulinum Toxin Injections
For spastic foot drop (often seen in stroke), botulinum toxin A:
- Reduces ankle spasticity
- Improves mobility when paired with physical therapy and stretching
5. Orthotic Devices (AFO)
AFOs are widely used to support foot positioning. While they provide immediate mechanical correction, they may alter gait patterns and cause discomfort or pressure points.
6. Rehabilitation
All patients, regardless of treatment type, benefit from targeted rehabilitation:
- Strengthening exercises
- Gait training
- Proprioception and balance therapy
- Stretching to maintain ankle mobility
Final Thoughts
Foot drop is a complex condition that significantly impacts quality of life. Many cases go underdiagnosed or undertreated due to a lack of standardized protocols. Whether the result of a nerve compression, stroke, or systemic condition, foot drop should trigger a thorough interdisciplinary assessment.
A coordinated approach involving neurosurgeons, orthopedic surgeons, physiotherapists, and rehabilitation experts can ensure that every patient receives both timely diagnosis and individualized care.
Dr. Mo Athar
