Common Causes of Foot Drop

Foot drop is a symptom or result of another underlying problem. Generally speaking, foot drop causes fall into one or a combination of three categories:

  • Muscle damage
  • Skeletal or anatomical abnormalities affecting the foot
  • Nerve damage
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Specific conditions and diseases that may lead to foot drop may include:

  • A lower back condition (see below for more detail)
  • A stroke or tumor
  • Parkinson’s disease
  • Diabetes
  • Motor neuron disease
  • Multiple sclerosis
  • Adverse reactions to drugs or alcohol
  • An injury to the foot or lower leg

The above list includes the most common causes of foot drop, but other possible sources of injury also occur. For example, it is possible for the peroneal nerve to become damaged during some types of hip replacement surgery, or as part of a dislocated knee injury.1

How the Lower Back Causes Foot Drop

There are a number of lower back problems that put pressure on the nerve leading to the peroneal nerve.

The peroneal nerve starts below the knee and runs along the outside of the leg. It runs down into the ankle, foot and the big toe and first toe. It is responsible for providing nerve sensation and communicating movement instructions to those areas. For example, the peroneal nerve connects to the muscles that allow the foot and toes to flex up (dorsiflexion).

Any impingement or damage to the peroneal nerve can cause foot drop.

Common lower back conditions that cause foot drop include:

  • Lumbar herniated disc. One of the most common causes of foot drop tends to be a herniated disc in the lower back (lumbar spine) that puts pressure on the nerve, or leads to inflammation in the nerve, that runs down the leg into the foot (the sciatic nerve). Pressure on the weak spot of the disc (located under the nerve root) may cause pain to nerves that connect with the sciatic nerve. Specifically, this pain will usually run below the knee and to the foot. When this happens, it is common for the foot pain to be accompanied by numbness and/or other neurological symptoms.
  • See Lumbar Herniated Disc: What You Should Know and
    What You Need to Know About Sciatica

  • Lumbar spinal stenosis. Spinal stenosis occurs when the spinal nerve roots are compressed or inflamed as a result of a number of possible factors, such as bone spurs, facet joint problems, and/or narrowing of the spinal canal. With lumbar spinal stenosis, nerve compression and/or inflammation can produce symptoms of pain, especially with activities involving standing and walking. Spinal stenosis tends to occur gradually over time, and is more common in people over age 60.
  • See Lumbar Spinal Stenosis: A Definitive Guide

  • Spondylolisthesis. This lower back condition is caused by a vertebra slipping forward over a lower vertebra, resulting in a pinched or inflamed nerve in the lower back. Again, depending on where the nerve is affected the symptoms can run all the way down to the foot.
  • See Degenerative Spondylolisthesis

  • Bone fractures or lacerations. A fracture to a vertebra in the lower back can cause stress and irritation to related nerves, leading to referred pain in the foot and possibly foot drop.

It should be known that while some foot drop treatments may be directed at symptoms, determining the underlying cause of foot drop is often necessary in order to effectively treat it.

References:

  1. Baima J, Krivickas L. Evaluation and treatment of peroneal neuropathy. Curr Rev Musculoskelet Med. 2008;1(2):147-53.
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Written by Grant Cooper, MD