Foot Drop Causes

When learning about foot drop, it should be reiterated that it is a symptom of an underlying condition. Generally speaking, foot drop causes may include:

  • Muscle damage
  • Skeletal or anatomical abnormalities affecting the foot
  • Nerve damage

Common Foot Drop Causes

Specific causes of foot drop that should be considered 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

This article focuses on the first cause, the specific lower back conditions that can cause foot drop.

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How the Lower Back Causes Drop Foot

There are a number of conditions in the lower back that put pressure on the nerve that leads to the peroneal nerve in the lower leg, which innervates the muscles that allow the foot to flex up.

When compromised, peroneal nerve damage may occur and prompt foot drop as a result of the following lower back problems:

  • Lumbar herniated disc. While there are many causes of foot drop, one of the most common cause tends to be a herniated disc in the lower back (lumbar spine) that is putting pressure on the nerve that runs down the leg and into the foot. Putting pressure on the weakest spot of the disc (located right under the nerve root), a herniated disc may prompt pain to nerves beyond the sciatic nerve (including the peroneal nerve) that is referred to the leg and foot. More specifically, this pain will usually run below the knee and to the foot, with the foot pain accompanied with numbness.
  • Spinal stenosis. Occurring gradually over time and usually in elderly patients, spinal stenosis occurs when the spinal nerve roots are compressed and choked as a result of a number of potential factors, most commonly enlarged facet joints (e.g. from osteoarthritis). With lumbar spinal stenosis, nerve compression can produce symptoms of pain, especially with activities involving standing and walking, and possibly foot drop.
  • Spondylolisthesis. Prompting an unstable and compromised spine segment as a result of a vertebra slipping forward over a lower vertebra, spondylolisthesis may result in a pinched nerve in the lower back.
  • Bone fractures or lacerations. A fracture to a vertebra in the lower back, such as from osteoporosis, can cause stress and irritation to related nerves, leading to referred pain in the foot and possibly foot drop. For anyone with who is diagnosed with or at risk for osteoporosis, a vertebral fracture should be considered as a possible cause of 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.

Written by Grant Cooper, MD