From the Guidelines
Piriformis syndrome is primarily caused by the compression or irritation of the sciatic nerve by the piriformis muscle, often due to anatomic variation or an associated fibrous band 1. This condition can result from various factors, including:
- Muscle spasms or tightness of the piriformis muscle
- Inflammation of the piriformis muscle
- Trauma to the buttock area
- Overuse or repetitive activities like running or climbing stairs
- Biomechanical abnormalities, such as abnormal gait patterns
- Anatomical variations where the sciatic nerve passes through the piriformis muscle rather than beneath it
- Poor posture
- Muscle imbalances in the hip region
- Activities that involve internal rotation of the hip
According to the study published in the Journal of the American College of Radiology 1, entrapment neuropathies, such as piriformis syndrome, are a common cause of lumbosacral plexopathy and can result from spinal or extraspinal compression. The clinical and electrodiagnostic features of lumbosacral plexopathy and radiculopathy often overlap, and imaging can help localize the site of nerve compression. Key points to consider in the diagnosis and management of piriformis syndrome include:
- Imaging studies, such as MRI, can be useful for detecting nerve abnormalities and/or neuromuscular variants associated with extraspinal nerve compression
- Treatment options may include physical therapy, stretching exercises targeting the piriformis muscle, anti-inflammatory medications, muscle relaxants, and activity modification to reduce irritation of the affected area.
From the Research
Causes of Piriformis Syndrome
- Piriformis syndrome is proposed to result from compression of the sciatic nerve, either in whole or in part, in the deep gluteal space by the piriformis muscle 2
- The compression of the sciatic nerve by the piriformis muscle is the primary cause of piriformis syndrome 3, 4, 5, 6
- The relationship between the anatomic finding of the sciatic nerve piercing the piriformis muscle and the syndrome is unclear, as this frequency is no different in those with the syndrome compared to healthy individuals 2
Risk Factors
- Buttock pain, external tenderness over the greater sciatic notch, and aggravation of the pain through sitting are common symptoms of piriformis syndrome 2, 4
- The prevalence of piriformis syndrome depends upon the diagnostic criteria being used and the population studied, but is estimated to be 5%-6% in all cases of low back, buttock, and leg pain and up to 17% of patients with chronic low back pain 2
Underlying Mechanisms
- Piriformis syndrome is a form of sciatica caused by compression of the sciatic nerve by the piriformis muscle 6
- The diagnosis of piriformis syndrome is complicated by the large differential diagnosis of low back and buttock pain with many diagnoses having overlapping symptoms 6
- The syndrome may be related to a myofascial condition rather than a focal neuropathy, as suggested by the lack of a uniformly accepted case definition and the unclear sensitivity and specificity of clinical signs 2