Piriformis syndrome (PS) is a painful musculoskeletal condition, characterized by a combination of symptoms including buttock or hip pain. In several articles, piriformis syndrome is defined as a peripheral neuritis of the branches of the sciatic nerve caused by an abnormal condition of the piriformis muscle (PM), such as an injured or irritated muscle.
Synonyms that are used frequently for PS are the deep gluteal syndrome, extra-spinal sciatica, wallet neuritis, etc. There are more women diagnosed with Piriformis syndrome than men, with a female–to–male ratio of 6:1. This ratio can be explained by the wider quadriceps femoris muscle angle in the os coxae of women.
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| Piriformis Syndrome |
Clinically Relevant Anatomy
The piriformis muscle (PM) originates from the pelvic surface of the sacral segments S2-S4 in the regions between and lateral to the anterior sacral foramina, the sacroiliac joint (superior margin of the greater sciatic notch), the anterior sacroiliac ligament and occasionally the anterior surface of the sacro-tuberous ligament. It passes through the greater sciatic notch to insert onto the greater trochanter of the femur.
The PM is functionally involved with external rotation, abduction and partial extension of the hip.
The sciatic nerve generally exits the pelvis below the belly of the muscle, however many congenital variations may exist.
The relationships between the PM and sciatic nerve have been classified by Beaton and Anson using a six category classification system. An anomalous relationship would be labelled between type ‘‘B’’ through type ‘‘F’’ since type ‘‘A’’ is considered to have a normal relationship between the PM and the sciatic nerve.
Variations in the relationship of the sciatic nerve to the piriformis muscle shown on the diagram above:
The sciatic nerve exiting the greater sciatic foramen along the inferior surface of the piriformis muscle; the sciatic nerve splitting as it passes through the piriformis muscle with the tibial branch passing;
Inferiorly or
Superiorly;
The entire sciatic nerve passing through the muscle belly;
The sciatic nerve exiting the greater sciatic foramen along the superior surface of the piriformis muscle. The nerve may also divide proximally, where the nerve or a division of the nerve may pass through the belly of the muscle, through its tendons or between the part of a congenitally bifid muscle.
Epidemiology /Aetiology
According to Boyajian- O’ Neill L.A. et al., there are two types of piriformis syndrome- primary and secondary.
Primary Piriformis Syndrome
Primary piriformis syndrome has an anatomical cause, with variations such as a split piriformis muscle, split sciatic nerve, or an anomalous sciatic nerve path. Among patients with piriformis syndrome, fewer than 15% of cases have primary causes. At present, there are no accepted values for the prevalence of the anomaly and little evidence to support whether or not the anomaly of the sciatic nerve causes piriformis syndrome or other types of sciatica. These findings suggest that piriformis and sciatic anomalies may not be as important to the pathophysiology of piriformis syndrome as previously thought.
Secondary Piriformis Syndrome
Secondary piriformis syndrome occurs as a result of a precipitating cause, including macrotrauma, microtrauma, ischemic mass effect, and local ischemia.
Piriformis syndrome is most often (50% of the cases) caused by macrotrauma to the buttocks, leading to inflammation of soft tissue, muscle spasms, or both, with resulting nerve compression.
Muscle spasms of the PM are most often caused by direct trauma, post-surgical injury, lumbar and sacroiliac joint pathologies or overuse.
PS may also be caused by shortening of the muscles due to the altered biomechanics of the lower limb, low back and pelvic regions. This can result in compression or irritation of the sciatic nerve. When there is a dysfunction of the piriformis muscle, it can cause various signs and symptoms such as pain in the sciatic nerve distribution, including the gluteal area, posterior thigh, posterior leg and lateral aspect of the foot.
Microtrauma may result from overuse of the piriformis muscle, such as in long-distance walking or running or by direct compression. An example of this kind of direct compression is known as “wallet neuritis”, which is a repetitive trauma caused by sitting on hard surfaces.
Aetiology of the piriformis syndrome
- Gluteal trauma in the sacroiliac or gluteal area
- Myofascial trigger points
- Hypertrophy and spasm of the piriformis muscle
- Secondary to laminectomy
- Abcess, hematoma, myositis
- Bursitis of the piriformis muscle
- Neoplasms in the area of the infrapiriform foramen
- Colorectal carcinoma Neurinoma of the sciatic nerve
- Episacroiliac lipoma
- Intragluteal injection
- Femoral nailing
- Myositis ossificans of the piriformis muscle
- Klippel-Trénaunay syndrome
Characteristics/Clinical Presentation
Patients with piriformis syndrome have many symptoms that typically consist of persistent and radiating low back pain, (chronic) buttock pain, numbness, paraesthesia, difficulty with walking and other functional activities such as pain with sitting, squatting, standing, with bowel movements and dyspareunia in women. Other characteristics include the following:
They can also have pressure pain in the buttock on the same side as the piriformis lesion and point tenderness over the sciatic notch in almost all instances. The buttock pain can radiate into the hip, the posterior aspect of the thigh and the proximal portion of the lower leg.
Swelling in the legs and disturbances of sexual functions have also been observed in patients with PS.
There may be an aggravation of pain with activity, prolonged sitting or walking, squatting, hip adduction and internal rotation and manoeuvers that increase the tension of the piriformis muscle.
Depending on the patient, the pain can lessen when lying down, bending the knee or when walking. However, some patients cannot tolerate the pain in any position and can only find relief when they’re walking.
Piriformis syndrome is not characterized by neurological deficits typical of a radicular syndrome, such as declined deep tendon reflexes and myotomal weakness.
The patient may present with a limp when walking or with their leg in a shortened and externally rotated position while supine. This external rotation while supine can be a positive piriformis sign, also called a splayfoot. It can be the result of a contracted piriformis muscle.
Differential Diagnosis
Piriformis syndrome can “masquerade” as other common somatic dysfunctions such as:
- Thrombosis of the iliac vein
- Trochanteric Bursitis
- Painful vascular compression syndrome of the sciatic nerve, caused by gluteal varicosities
- Herniated intervertebral disc
- Post-laminectomy syndrome or coccygodynia
- Posterior facet syndrome at L4-5 or L5-S1
- Unrecognized pelvic fractures
- Lumbar osteochondrosis
- Undiagnosed renal stones
- Lumbosacral radiculopathies
- Osteoarthritis (lumbosacral spine)
- Sacroiliac joint syndrome
- Degenerative disc disease
- Compression fractures
- Intra-articular pathology in the hip joint: labral tears, femuro-acetabular impingement (FAI)
- Lumbar spinal stenosis
- Tumours, cysts
- Gynaecological conditions
- Diseases such as appendicitis, pyelitis, hypernephroma, uterine disorders, prostate disorders and malignancies in pelvic viscera.
- Dysfunction, lesion and inflammation of sacroiliac joint
- Pseudoaneurysm in the inferior gluteal artery following gynaecological surgery
- Sacroiliitis
- Psychogenic disorders: physical fatigue, depression, frustration
Investigations
Piriformis syndrome continues to be a controversial diagnosis for sciatic pain.
Radiographic studies have limited application to the diagnosis of piriformis syndrome. Although standard anteroposterior radiographs of the pelvis and hips, lateral views of the hips and either CT or MRI of the lumbar spine are recommended to rule out the possibility that the symptoms experienced by the patients originate from the spine or the hip joint.
Electromyography (EMG) may be also beneficial in differentiating piriformis syndrome from other possible disorders, such as intervertebral disc herniation. Interspinal nerve impingement will cause EMG abnormalities of muscles proximal to the piriformis muscle. In patients with piriformis syndrome, however, EMG results will be normal for muscles proximal to the piriformis muscle and abnormal for muscles distal to it. Electromyography examinations that incorporate active manoeuvers, such as the FAIR test, may have a greater specificity and sensitivity than other available tests for the diagnosis of piriformis syndrome.
Electrophysiological testing and nerve blocks play important roles when the diagnosis is uncertain. Injection of local anaesthetics, steroids, and botulinum toxin into the piriformis muscle can serve both diagnostic and therapeutic purposes.
Outcome Measures
Roland-Morris Disability Questionnaire
Examination
A complete neurological history and physical assessment of the patient is essential for an accurate diagnosis. The physical assessment should include the following points:
Observation
Patients with piriformis syndrome may also present with gluteal atrophy, as well as shortening of the limb on the affected side.In chronic cases, muscle hypotrophy is present in the affected extremity.
Palpation
The patient reports sensitivity during palpation at the greater sciatic notch, in the region of sacroiliac joint or over the piriformis muscle belly. It is possible to detect the spasm of the PM by careful, deep palpation.
With deep digital palpation in the gluteal and retro-trochanteric area, there may be tenderness and pain with an exacerbation of tightness and leg numbness.
Pace sign
Pace’s sign consists of pain and weakness by resisted abduction and external rotation of the hip in a sitting position. A positive test occurs in 46.5% of the patients with piriformis syndrome.
Lasèque sign / Straight Leg Raise Test
The patient reports buttock and leg pain during passive a straight leg raise performed by the examiner.
Involves pain and weakness on passive forced internal rotation of the hip in the supine position. The pain is thought to be a result of passive stretching of the piriformis muscle and pressure placed on the sciatic nerve at the sacrospinous ligament. Positive in 56,2% of the patients.
FAIR
Painful flexion-adduction-internal rotation
Beatty’s Manoeuver
An active test that involves elevation of the flexed leg on the painful side, while the patient is lying on the asymptomatic side. The abduction causes deep buttock pain in patients with PS, but back and leg pain in patients with lumbar disc disease.
The Hughes test
External isometric rotation of the affected lower extremity following maximal internal rotation may also be positive in PS patients.
Hip Abduction Test
The patient lies on the side with lower leg flexed to provide support and the upper leg straight, in line with the trunk. The practitioner stands in front of the patient at the level of the feet and observes (no hands-on) as the patient is asked to abduct the leg slowly.
Normal – Hip abduction to 45°.
Abnormal – if hip flexion occurs (indicating TFL shortness) and/or leg externally rotates (indicating piriformis shortening) and/or ‘hiking’ of the hip occurs at the outset of the movement (indicating quadratus overactivity and therefore, by implication, shortness)
Trendelenburg Sign
Trendelenburg sign may also be positive.
Medical Management
Conservative treatment for piriformis syndrome includes pharmacological agents [non-steroidal anti-inflammatory agents (NSAIDs), muscle relaxants and neuropathic pain medication], physical therapy, lifestyle modifications and psychotherapy.
Injections of local anaesthetics, steroids, and botulinum toxin into the PM muscle can serve both diagnostic and therapeutic purposes. The practitioner should be familiar with variations in the anatomy and the limitations of landmark-based techniques. An ultrasound-guided injection technique has recently been utilized. This technique has been shown to have both diagnostic and therapeutic value in the treatment of PS.
Piriformis syndrome often becomes chronic and pharmacological treatment is recommended for a short time period.
Surgical Management
Surgical interventions should be considered only when nonsurgical treatment has failed and the symptoms are becoming intractable and disabling. Classic indications for surgical treatment include abscess, neoplasms, hematoma, and painful vascular compression of the sciatic nerve caused by gluteal varicosities.
Surgical release with tenotomy of the piriformis tendon to relieve the nerve from the pressure of the tense muscle has resulted in immediate pain relief, as reported by several authors.
Sometimes, the obturator internus muscle should be considered as a possible cause of sciatic pain. However, the diagnosis of the obturator internus syndrome can only be made by ruling out other possible causes of sciatic pain, which is similar to the manner in which piriformis syndrome is diagnosed. Surgical release of the internal obturator muscle can result in both a short- and long-term reduction in pain in patients with retro-trochanteric pain syndrome and should be considered if conservative treatment fails.
The postoperative management consists of partial weight-bearing using crutches for 2 weeks and unrestricted range of motion exercises. The above surgical approach has shown promising short-term results
The treatment algorithm for retro-trochanteric pain syndrome:
Physical Therapy Management
Although there is a paucity of recently published controlled trials in which critically examine the effectiveness of the noninvasive management modalities, a number of methods exist for the treatment of ‘Piriformis Syndrome’.
The non-invasive treatments include physical therapy, (osteopathic) manipulative treatment and lifestyle modification. The use of Ozone Therapy can be considered in the management of PS, due to the absence of side effects, the practicality of use and the extent of clinical improvement.
According to Tonley et al., the most commonly reported physical therapy interventions include ultrasound, soft tissue mobilization, piriformis stretching, hot packs or cold spray and various lumbar spine treatments. In addition, Tonley et al. describe an alternative treatment approach for piriformis syndrome. The intervention focused on functional exercises Therapy Exercises for the Hip aimed at strengthening the hip extensors, abductors and external rotators, as well as correction of faulty movement patterns. Despite positive outcomes full resolution of low back pain, cessation of buttock and thigh pain in the single case report care must be taken in establishing cause and effect based on a single patient.
To achieve a 60 – 70% improvement, the patient usually follows 2 – 3 treatments weekly for 2-3 months.
First of all, the patient must be placed in the contralateral decubitus and FAIR position (Flexed Adducted Internally Rotated). Start with an ultrasound treatment: 2.0-2.5 W/cm2, for 10-14 minutes. Apply the ultrasound gel in broad strokes longitudinally along the piriformis muscle from the conjoint tendon to the lateral edge of the greater sciatic foramen
Before stretching the piriformis muscle, treat the same location with hot packs or cold spray for 10 minutes. The use of hot and cold before stretching is very useful to decrease pain.
After that, begin with stretching of the piriformis which can be executed in a variety of ways. Stretch the piriformis muscle by applying manual pressure to the muscle’s inferior border.
It is important not to press downward, rather directing pressure tangentially, toward the ipsilateral shoulder. When pressing downward, the sciatic nerve will compress against the tendinous edge of the gemellus superior. However, when applying tangential pressure, the muscle’s grip will weaken on the nerve and relieve the pain of the syndrome. (18, Fischman et al. (2002), level of evidence A2), Another way to stretch this muscle is in the FAIR position. The patient lies in a supine position with the hip flexed, adducted and internally rotated. Then the patient brings his foot of the involved side across and over the knee of the uninvolved leg.
We can enhance the stretch, by letting the physical therapist perform a muscle–energy technique. This technique involves the patient abducting his limb against light resistance, which is provided by the therapist for 5-7 seconds, with 5-7 repetitions.
After stretching, continue with myofascial release at the lumbosacral paraspinal muscles and McKenzie exercises. When the patient lies in the FAIR position, the lumbosacral corset can be used.
PS is caused when the tight piriformis is forced to do the work of other large muscles (like the gluteus maximus, the gluteus medius), An alternative treatment approach for piriformis syndrome using a hip muscle strengthening program especially of the weak gluteal musculature with movement re-education can help in pain relief
The therapist can also give several tips to avoid an aggravation of the symptoms. This includes:
- Avoid sitting for a long period; stand and walk every 20 minutes,
- Make frequent stops when driving to stand and stretch.
- Prevent trauma to the gluteal region and avoid further offending activities.
- Daily stretching is recommended to avoid the recurrence of the piriformis syndrome.
Home exercises
- The patient can also perform several exercises and treatments at home including:
- Rolling side to side with flexion and extension of the knees while lying on each side
- Rotate side to side while standing with the arms relaxed for 1 minute every few hours
- Take a warm bath
- Lie flat on the back and raise the hips with your hands and pedal with the legs like you are riding a bicycle.
- Knee bends, with as many as 6 repetitions every few hours.
Clinical Bottom Line
Piriformis syndrome (PS) is a painful musculoskeletal condition and is most often caused by macrotrauma to the buttocks, leading to inflammation of soft tissue, muscle spasms, or both, with resulting nerve compression. Patients with piriformis syndrome have many symptoms that typically consist of persistent and radiating low back pain, (chronic) buttock pain, numbness, paraesthesia, difficulty with walking and other functional activities.
Piriformis syndrome continues to be a controversial diagnosis for sciatic pain. A complete neurological history and physical assessment of the patient is essential for an accurate diagnosis. Optimizing the therapeutic approach requires an interdisciplinary evaluation of treatment.
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