This article is divided into several pages for easier reading:

1.0     Introduction

Piriformis syndrome is a condition in which the piriformis muscle, located in the buttock region, spasms and causes buttock pain. The piriformis muscle can also irritate the nearby sciatic nerve and cause pain, numbness and tingling along the back of the leg and into the foot (similar to sciatic pain).

The piriformis muscle inserts at the sacrum and terminates at the femoral greater trochanter, providing hip mobility through lateral rotation and abduction. Piriformis syndrome results from the sciatic nerve being compressed by the piriformis muscle. This syndrome is clinically diagnosed through isolation of the source of pain and elimination of any other identifiable cause.

Piriformis syndrome is often confused with other conditions, especially lumbar spine conditions. Attaining a proper diagnosis of piriformis syndrome is important when considering treatment for low back and leg pain.

The first description was made by Yeoman in 1928 (Yeoman, 1928), with Freiberg and Vinke recognising specific signs in 1934 (Freiberg & Vinke, 1934). However, the credit for making this pure nerve compression syndrome into a true disease entity, and for naming it, goes to Robinson in 1947 (Robinson, 1947).

And, although it has been discussed for a long time, it is currently (sort of) recognised as a genuine compression neuropathy due to clinical, anatomical, and electrical studies and because of the progress in modern imaging. Over the last few years there has been an increase in publications, especially in terms of information from magnetic resonance imaging (MRI) and regarding non-surgical treatment options.

However, even up to 2013, it was reported that there was no definitive proof that piriformis syndrome existed (Halpin & Ganju, 2009; Jankovic, Peng & van Zundert, 2013). In 2001, one academic even published a paper titled ‘The “Piriformis Syndrome”–Myth or Reality?” (McCrory, 2001).

This article is divided into eleven parts for easier reading. Part One is this introduction and defining terms. Part Two of this overview will provide the reader with some definitions of Piriformis syndrome, and other common terms by which it is known. Section Three will then provide a description of the gluteal region, including the Piriformis muscle and sciatic nerve. Section Four will outline the causes of Piriformis syndrome, why it is a problem and some of the known complications. Section Five will describe who can be affected by the condition and Section Six the prevalence and risk factors, as well as highlighting some of the inaccuracies across the studies. Section Seven will look at the symptoms across the identified populations affected by the condition before Section Eight describes how the condition is diagnosed and measured. Section Nine outlines some of the conditions which are similar to Piriformis syndrome which the reader should be wary of. Section Ten provides a comprehensive overview of the treatments available such as physiotherapy, exercise and surgical interventions. Nearing the end, Section Eleven highlights the outlook for people with the condition. Sections Twelve and Thirteen provide the references and bibliography respectively.

1.1     Defining the Terms

For those readers with little or no knowledge of medical terms, the following will help when reading the article.

  • Piriform (Pyriform): Having the form of a pear.
  • Gluteal: Of or relating to the gluteus muscles.
  • Gluteus: Any of the large muscles of the buttocks.
  • Superficial Muscle: In anatomy, on the surface or shallow – as opposed to deep.
  • Deep Muscle: In anatomy, away from the surface or further into the body – as opposed to superficial.
  • Gluteus Maximus: Is a superficial muscle of the hip that forms most of the flesh of the buttock, and is the largest muscle of the gluteus muscle group – the other two being the gluteus medius and gluteus minimus.
  • Sciatic Nerve: Is the largest nerve in the body. It splits to common fibular and tibial nerves.
  • Sciatica: Pain along the course of a sciatic nerve especially in the back of the thigh.
  • Sacroiliac Joint: The sacroiliac joints are weight-bearing, compound joints consisting of an anterior synovial joint between the auricular surfaces of the sacrum and ilium and a posterior syndesmosis between the tuberosities of the same bones.
  • Lumber Disc Herniation: A common cause of lower back and leg pain is a lumbar ruptured disc or herniated disc. Symptoms of a herniated disc may include dull or sharp pain, muscle spasm or cramping, sciatica, and leg weakness or loss of leg function. Sneezing, coughing, or bending usually intensify the pain.
  • Sacroiliac Joint Dysfunction: An asymmetry in the sagittal plane between the two halves of the pelvis (ilia or innominate bones).
  • Spasm: A sudden involuntary muscular contraction or convulsive movement.
  • Gluteal Fold: The gluteal sulcus (also known as the gluteal fold, fold of the buttock or horizontal gluteal crease) is an area of the body of humans and great apes, described by a horizontal crease formed by the inferior aspect of the buttocks and the posterior upper thigh.
  • Neuropathy: Damage, disease, or dysfunction of one or more nerves especially of the peripheral nervous system that is typically marked by burning or shooting pain, numbness, tingling, or muscle weakness or atrophy, is often degenerative, and is usually caused by injury, infection, disease, drugs, toxins, or vitamin deficiency.
  • Peripheral nervous system (PNS): The part of the nervous system that is outside the central nervous system and comprises the cranial nerves excepting the optic nerve, the spinal nerves, and the autonomic nervous system.
  • Central nervous system (CNS): the part of the nervous system which (in vertebrates) consists of the brain and spinal cord, to which sensory impulses are transmitted and from which motor impulses pass out, and which coordinates the activity of the entire nervous system.
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