Foot drop

Foot drop — also called drop foot — is the inability or difficulty to raise the front part of the foot (ankle dorsiflexion). Rather than a disease in itself, it is a symptom of an underlying problem affecting the neurological, muscular, or anatomical structures that control foot lifting.

The key muscles involved are the ankle dorsiflexors — primarily the tibialis anterior — which are controlled by the common peroneal (fibular) nerve, a branch of the sciatic nerve. Damage anywhere along the pathway from the brain to the peroneal nerve produces weakness in these muscles and the characteristic foot drop.

**Causes:**

*Nerve injury (most common):* - Compression of the common peroneal nerve at the fibular neck (the nerve passes superficially here and is vulnerable to prolonged leg crossing, squatting, or plaster cast pressure) - Nerve root compression in the lumbar spine (L4–L5 disc herniation causing L5 radiculopathy) - Damage to the peroneal nerve during hip or knee replacement surgery - Peripheral neuropathy (diabetic neuropathy, Charcot-Marie-Tooth disease)

*Muscle disorders:* - Muscular dystrophy - Inflammatory myopathy

*Central nervous system disorders:* - Stroke (affecting the motor cortex or corticospinal tract) - Multiple sclerosis - Amyotrophic lateral sclerosis (ALS) - Spinal cord injury or tumour - Brain tumour

**Symptoms and gait characteristics:** - Inability to lift the front of the foot when walking — the foot or toes drag along the ground - Compensatory high-stepping gait (steppage gait) — the patient lifts the knee excessively to clear the foot from the floor, mimicking someone climbing stairs - Foot slap — the foot comes down flat or heel-last with an audible slap - Instability on uneven surfaces and increased risk of falls and trips - Numbness or tingling on the top of the foot and between the first two toes (if the peroneal sensory branch is affected)

**Diagnosis** requires identifying the level of the lesion — peripheral nerve (EMG/nerve conduction studies), nerve root (MRI of the lumbar spine), or central (MRI of the brain or spinal cord). EMG can distinguish between a peroneal nerve lesion and an L5 radiculopathy.

**Treatment:** - *Treat the underlying cause:* decompress a compressed peroneal nerve; treat the disc herniation; manage the stroke or MS - *Ankle-foot orthosis (AFO):* a brace holding the foot in a neutral position, enabling safer, more energy-efficient walking - *Physiotherapy:* stretching of the heel cord (to prevent equinus contracture), strengthening of residual dorsiflexors, gait retraining, and balance training - *Functional electrical stimulation (FES):* surface electrodes applied over the peroneal nerve stimulate dorsiflexion with each step — restores near-normal gait in suitable patients - *Neuromodulation:* rTMS and tDCS targeting the motor cortex can augment neurological recovery after central lesions - *Surgery:* peroneal nerve decompression or neurolysis for compressive injuries; tendon transfer (tibialis posterior) for permanent foot drop with no neurological recovery expected