Foot Drop

🦶 Foot Drop is the inability to dorsiflex the foot due to weakness of the tibialis anterior. It usually arises from lesions of the common peroneal nerve or L5 nerve root, but many neurological and systemic conditions can cause it. Patients often present with a high-steppage gait to avoid tripping.

🚨 Causes of Foot Drop

• 🧠 CNS: Stroke, Multiple Sclerosis, Motor Neuron Disease (ALS).
• 🦵 Nerve Root: L5 radiculopathy (commonly due to lumbar disc herniation).
• 🩻 Peripheral Nerve: Peroneal nerve compression (leg crossing, fibular head trauma, casts).
• 🧬 Genetic/Neuromuscular: Charcot-Marie-Tooth disease (progressive neuropathy, high arches).
• 🍬 Metabolic: Diabetic neuropathy (chronic sensory-motor polyneuropathy).
• 🩺 Trauma/Surgery: Hip or knee surgery, fractures causing direct nerve injury.

🩺 Clinical Features

• 👣 Gait: High-steppage gait (lifting the knee higher than normal).
• ⚡ Weakness: Inability to dorsiflex ankle or extend toes.
• 🔎 Sensation: Numbness over dorsum of foot (peroneal nerve) or posterolateral leg (L5).
• 🧩 Other signs: Fasciculations (MND), spasticity (MS/stroke), high arches (CMT).

🔬 Assessment

• 📖 History: Recent trauma, back pain, systemic illness, family history.
• 🩺 Exam: Test dorsiflexion, inversion/eversion, sensation, reflexes.
• 📊 Investigations:
  • EMG & Nerve Conduction Studies – localise lesion.
  • MRI Lumbar Spine – L5 radiculopathy.
  • MRI/CT Brain – stroke, MS.
  • Limb Imaging – trauma, compression.
  • Bloods – HbA1c, ferritin, autoimmune screen if relevant.

📋 Differential Diagnosis & Management

💡 Clinical Tip

Always look for “high-steppage gait” in suspected foot drop. It’s the classic OSCE clue - patients exaggerate hip/knee flexion to clear the toes.

Cases - Foot Drop

• Case 1 - Common Peroneal Nerve Palsy 🦵: A 28-year-old man develops acute foot drop after a long day of squatting while painting. Exam: weakness of ankle dorsiflexion and eversion, sensory loss over dorsum of foot. Diagnosis: Compression neuropathy of common peroneal nerve at fibular head. Management: Remove compression, ankle–foot orthosis (AFO), physiotherapy; recovery usually good.
• Case 2 - L4/L5 Radiculopathy (Lumbar Disc Prolapse) 💥: A 45-year-old warehouse worker presents with severe back pain radiating down the lateral leg, followed by sudden left foot weakness. Exam: foot drop, positive straight leg raise, reduced ankle reflex. Diagnosis: L4/L5 nerve root compression from lumbar disc herniation. Management: Analgesia, physiotherapy; urgent neurosurgical review if progressive or with cauda equina features.
• Case 3 - Motor Neuron Disease (ALS) 🧠: A 58-year-old man develops insidious bilateral foot drop. Exam: fasciculations in calves, mixed UMN + LMN signs, brisk reflexes despite weakness. Diagnosis: Motor neuron disease (ALS). Management: MDT care (neurology, physio, OT), riluzole, supportive orthotics.
• Case 4 - Stroke (UMN Lesion) 🧩: A 72-year-old woman presents with sudden right hemiparesis following a left MCA stroke. On recovery, she is left with persistent right-sided foot drop and circumduction gait. Diagnosis: Upper motor neuron foot drop from cortical stroke. Management: Stroke rehab, AFO, functional electrical stimulation, physio.
• Case 5 - Charcot–Marie–Tooth (Hereditary Neuropathy) 🧬: A 20-year-old man has long-standing high-arched feet (pes cavus) and difficulty dorsiflexing his ankles. Exam: bilateral foot drop, distal wasting, absent ankle reflexes. Diagnosis: Hereditary motor and sensory neuropathy (CMT). Management: Supportive - orthotics, physiotherapy, genetic counselling.

Teaching Commentary 🧠

Foot drop = weakness of dorsiflexion, leading to high-stepping gait. Causes can be divided into: - Peripheral nerve (common peroneal compression, trauma). - Radiculopathy (L4/L5 disc disease). - Neuromuscular (CMT, muscular dystrophies). - Motor neuron disease. - CNS lesions (stroke, MS, spinal cord disease). Clinical localisation depends on associated features (reflexes, pattern of weakness, sensory changes). Management = treat cause + supportive orthotics and rehab.