Foot pain due to Sciatica

Sciatica is a debilitating condition in which the person experiences radiating pain in one leg that passes beyond the knee, including as far as the foot. Sciatica may present with or without neurological symptoms such as paraesthesia (“pins and needles”) or muscle weakness along with pathway of the sciatic nerve or its branches. As such, people can have sciatica without these symptoms. Some people with sciatica may have accompanying back pain although this pain is usually less than the pain in the leg itself.

It is a mistake to use the term “sciatica” to refer to any pain starting in the lower back and going down the leg. Sciatica involves pain that goes beyond the knee. There are many other causes of lower back and leg pain that do not meet the criteria for being diagnosed as “sciatica”. Sciatica can be caused by a disturbance to any part of the sciatic nerve, although 85% of cases are the result of a vertebral disc disorder and the resulting impingement or inflammation of one or more spinal nerve roots or sensory ganglia. The two most common disc disorders that can cause sciatica are lumbar vertebral disc ruptures (e.g. herniated disc) and spinal stenosis (degeneration of the vertebrae due to injury, degenerative bone disorders such as osteoarthritis, and inflammatory diseases). Other causes include spondylolisthesis (vertebrae moving out of place relative to adjacent vertebrae), spinal or paraspinal masses (e.g. abscesses, tumours, epidural haematomas), piriformis syndrome, pregnancy, tumours in the pelvic cavity, and disturbances at the proximal biceps femoris muscle.

Sciatica affects approximately 1-5% of people each year, with 10-40% of people experiencing sciatica at some point in their lifetimes. Sciatica is rare in people under 20 years of age (unless due to trauma) with a peak incidence between 40 and 60 years of age. Physical activity increases the risk in people who have had sciatica before and reduces the risk in people who have never had sciatica.

Sciatica may begin suddenly, often during physical activity, or it may develop slowly. People with sciatica often describe the pain as “aching”, “sharp” and “shooting”. The pain of sciatica usually follows the dermatome or dermatomes of the affected spinal nerve root or roots. The sciatic nerve consists of the spinal nerve roots from the 4th and 5th lumbar vertebrae and the 1st, 2nd, and 3rd sacral foramen. Sciatica usually involves pathology of the 4th and 5th lumbar and 1st sacral foramen. Pathology involving the spinal nerves of 2nd and 3rd sacral foramen are less common. Sciatica involving the 4th lumbar vertebrae may easily be misdiagnosed as a hip condition, as the pain radiates to the anterior-lateral aspect of the thigh. For some people, sciatic pain can occur when coughing, sneezing or straining, which may indicate a disc rupture.

It is important that podiatrists not confuse sciatica with other neurological causes of foot pain such as entrapment of the sural nerve or Tarsal Tunnel Syndome, as these may respond to treatments we offer, while sciatica is unlikely to.

The sciatic nerve is the largest branch of the sacral plexus and runs alongside the hip and downward through the leg and through its terminal branches, into the foot. As previously mentioned, it is formed from 5 spinal nerves (L4-S3) which coalesce in the pelvis deep to piriformis (in most people) to form the sciatic nerve. The nerve then passes through the greater sciatic foramen of the pelvis and into the upper leg. From here, it passes inferiorly through the posterior thigh and to the popliteal fossa behind the knee. Here it divides into 2 branches, the tibial nerve and the common peroneal nerve (sometimes called the common fibular nerve). The tibial nerve moves inferiorly through the posterior compartment of the lower leg to the heel. Here it divides into the medial and lateral plantar nerves and their branches. The common peroneal (fibular) nerve moves inferiorly through the anterior and lateral compartments of the lower leg and is subdivided into the superficial and deep peroneal nerves.

The sciatic nerve is by far the thickest nerve in the body and can be up to 2cm in diameter. It is also the longest nerve.

Below of an illustration of the dermatomes of the leg, including those associated with the sciatic nerve (L4 – S3) and thus affected by sciatica. Please observe the distribution of L4-S1 as these are most commonly affected in cases of sciatica. The areas of skin marked L4-S3 are also innervated by the sciatic nerve and thus the sensations of the skin in these areas are mediated via the sciatic nerve.

Dermatomes of the foot (note L4, L5, S1)

The sciatic nerve directly innervates the muscles of the posterior compartment and the lateral rotator group of the upper leg (except piriformis and gradratus femoris) and indirectly innervates the posterior compartment of the lower leg through the tibial nerve branch and the anterior and lateral compartment muscles through the common peroneal branches, as well as the intrinsic muscles of the foot, mostly though the medial and lateral branches of the tibial nerve and the extensor digitorum brevis through the deep peroneal nerve.

It is important to be aware of other conditions that may present with similar symptoms as sciatica. These include clauda equina syndrome, spinal fractures, cancer and infection. If someone has any other symptoms that may accompany these conditions, then they should be referred for further investigation. NICE guidelines recommend urgent referrals if people present with sciatica-like symptoms and also have any of the following:

  1. Bowel or bladder disturbances (most often reduced urination).
  2. Progressive or severe bilateral neurological weakness (major motor weakness affecting knee extension, ankle eversion, or foot dorsiflexion).
  3. Loss of sensation in the perineal, perianal or genital areas.
  4. Bilateral sciatica.
  5. Incapacitating pain.
  6. Unrelenting night pain.
  7. Use of steroids or intravenous drugs.

Diagnosis is usually based on history and presenting symptoms. A few tests may also be carried out, most notably the Straight Leg Raise Test (with or without dorsiflexion of the foot at the ankle joint) and the Bow Test. Treatment in the early stages is usually very conservative. Many people with sciatica will improve within a few weeks, and many will resolve naturally within 8-9 months. After a diagnosis of sciatica is made, the patient may be offered medication, usually NSAIDs (non-steroidal anti-inflammatory drugs), manual therapy, and therapeutic exercises. If the person’s condition remains unchanged or worsens after several weeks, then further examination and imaging may be used to diagnose the underlying cause. Surgery may be indicated depending on what the underlying cause is. The use of opioid drugs, anti-epileptic drugs, benzodiazipines, and oral corticosteroids is not usually recommended as there is little evidence to support their use for this condition and evidence that they can cause harm. Psychological therapies may be offered alongside physical therapies.

According to the BMAS (British Medical Acupuncture Society), medical acupuncture can also be used to help manage the pain associated with sciatica, although this may require 2-3 sessions per week for several weeks. While manual acupuncture may be helpful in some cases, stronger treatments, such as electro-acupuncture or strong dry needling techniques may be needed, although this does not reduce the need for 2-3 sessions per week. While acupuncture may not deal with the causes of sciatica, such as nerve impingement or space-occupying lesions, it may help manage the symptoms of pain, allowing the patient to participate in the therapeutic exercises they have been given, along with other exercise, thereby having an indirect beneficial effect on the outcome of the condition.

Podiatrists are not usually considered for referral for people with sciatica, although we often see them in clinic for other conditions they may have. It is important to note that most of the treatments podiatrists offer, including in-shoe orthoses, either pre-fabricated or bespoke, may have little or no effect on this condition. Usually the best support we can offer is compassion and a referral for further examination.

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