Introduction. Not all low back, hip, and gluteal (buttock) pain are manifestations of back injury. Pain in any of these areas may indicate injury or irritation of any one of a number of muscles and nerves surrounding the low back and hip. Injury to any of these structures can result in pain and loss of function. A specific muscle that is susceptible to injury and inflammation is the piriformis muscle. Due to the location of this muscle, the sciatic nerve is often involved with piriformis problems. Pain and dysfunction resulting from piriformis injury is referred to as piriformis syndrome. The symptoms of this disorder sometimes mimic those of a bulging lumbar disc, or similar low back injury. Therefore, diagnosis of pain in the low back, gluteal, or hip region should include an evaluation of the piriformis muscle (PM), other hip musculature, and surrounding nerves.
Anatomy and Function. The piriformis muscle is located deep in the gluteal region. This muscle attaches to the sacrum and the lateral portion of the upper part of the femur. It is one part of a group of muscles whose actions include abduction (moving the thigh away from the midline) and external rotation of the thigh (turning the knee and toes outward). These muscles are important in maintaining stability of the hip in all weight bearing activities.
The sciatic nerve passes between the piriformis muscle and a notch in the pelvis as it enters the gluteal region. This large nerve supplies a majority of the nervous innervation to the lower extremity. In some cases, the PM may be split into two bellies, with the sciatic nerve passing in between the two portions. The sciatic nerve also may be split into two trunks which may pass through different portions of the PM (1). In any of these arrangements, the sciatic nerve is susceptible to compression between the piriformis and the pelvis.
The PM is susceptible to hypertrophy, an increase in size, as a result of its high level of activation. With increased use, muscles increase size and strength. During the weight bearing portion of gait, the piriformis is lengthened which initiates a stretch reflex and results in contraction. During the swing phase of gait, the piriformis contracts again to assist with external rotation (1). This double activation may precipitate muscular hypertrophy, thereby decreasing the space available for the sciatic nerve.
Symptoms and Diagnosis. Symptoms of piriformis syndrome often include deep buttock and posterior hip pain. The gluteal discomfort may be accompanied by pain, numbness, and tingling, that radiates into the posterior thigh, leg, and foot. These symptoms are generally associated with a condition known as sciatica. Sciatica pain is often the result of nerve compression in the spinal cord associated with a herniated lumbar disc (2,3). Generally this type of low back injury also will be accompanied by neurological deficits that are absent with piriformis syndrome.
The pain and discomfort of piriformis syndrome are usually exacerbated by standing after prolonged sitting and with activity. Pain is minimized when lying down with the hips slightly flexed, in a curled up position. Tightness and sensitivity may be revealed during palpation of the PM. The PM is stretched when the body is rotated around a planted foot, as in a tennis serve. This motion will reproduce pain. Resisted abduction in the seated position should reproduce discomfort in the PM.
Diagnosis of piriformis syndrome may be delayed or missed completely without a thorough examination. Often, piriformis syndrome is diagnosed after other causes of sciatica have been ruled out (2,3).
Suggested etiology of piriformis syndrome begins with injury to the PM or the pelvis. Trauma to the PM may result in spasm, edema, contracture, and finally compression and entrapment of the sciatic nerve (1). Hypertrophy or extreme tightness of the piriformis also may compress the sciatic nerve. Piriformis tightness can result from increased lumbar lordosis, swayed low back, and concurrent hip flexor tightness (4). Improper biomechanics, muscle imbalance, and leg length discrepancies may contribute to piriformis problems.
Treatment. Although there appear to be numerous causes of piriformis syndrome, the treatment approach follows a consistent pattern. Treatment of piriformis syndrome should focus on reducing the compression of the sciatic nerve. If compression is the result of inflammation of the PM and or the sciatic nerve, ice can be effective in reducing edema and pain. Ice should be applied directly over the piriformis muscle, which lies just beneath the hip dimple, for 20 to 30 minutes several times per day. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen can help control inflammation and pain (4). Rest also may be indicated in order to prevent re-injury.
Passive stretching of tight musculature, too, is important in restoring normal range of motion and function. The correction of biomechanical errors and leg length discrepancies are important (1,4,5). Through gait analysis and physical examination, an athletic trainer, physical therapist, podiatrist, or physician can diagnose gait errors, muscle imbalance, and limb length discrepancies. Muscle strengthening and body mechanics education can correct the biomechanical errors while the prescription of foot orthoses can compensate for leg length differences. Achievement of a normal range of motion should be the first goal. Once adequate range of motion is acquired, strengthening exercises may then be added to correct any muscle imbalances. If these conservative treatments of ice, NSAIDs, stretching, and biomechanical corrections, are ineffective, corticosteroid injections may be prescribed. In extremely resistant cases, surgical release of the piriformis muscle may be indicated.
Stretching protocols involve hip flexion, adduction, and internal rotation applied with slow steady pressure. Once inflammation has been resolved, heat modalities such as ultrasound, whirlpool, and moist heat can be used prior to stretching to improve the elasticity of the tissues being stretched. The application of ultrasound should be supervised by a physical therapist or athletic trainer. Moist heat can be applied over the PM and proximal musculature for 15 minutes. A cloth should be placed between the skin and the heat pack to protect against burning. Maintaining normal range of motion will help alleviate symptoms, as well as prevent progression and recurrence of symptoms.
Correction of biomechanical and training errors are also important in the treatment and prevention as are leg length discrepancies and muscle imbalances. As stated earlier, there are a number of health professionals who can assess the structure and function of the hip and lower extremity. Abnormalities in any of the components of gait: limb length, joint range of motion, muscle function, strength balance, and coordination of movement, can result in added stress on the piriformis muscle. A controlled program of stretching, strengthening, and mechanic education with the correction of structural problems can help to alleviate symptoms and prevent recurrence. Alternative methods of training may also be helpful. Aquatic therapy, changes in the regular running surface, and a change in training volume are options that could be considered.
In determining the diagnosis for low back, gluteal, hip, and lower extremity pain the examination should include an assessment of piriformis health and function. Pain resulting from compression of the sciatic nerve by the PM sciatic nerve can be managed and prevented from recurring. Inflammation can be reduced with ice, NSAIDs, and rest. Further treatment of hypertrophy and tightness includes stretching protocols and correction of biomechanical and structural abnormalities. Education regarding the progression of the disorder also may help the individual manage and limit the recurrence of piriformis syndrome.
References.
(1) Julsrud, M. E. (1989). Piriformis syndrome. Journal of the American
Podiatric Medical Association, 79, 128-131.
(2) Chen, W. S. (1992). Sciatica due to piriformis pyomyositis. The Journal of
Bone and Joint Surgery, 74-A, 1546-1548.
(3) Vandertop, W. P., and Bosma, N. J. (1991). The piriformis syndrome. The
Journal of Bone and Joint Surgery, 73-A, 1095-1097.
(4) Keskula, D. R. and Tamburello, M. (1992). Conservative management of
piriformis syndrome. Journal of Athletic Training, 27, 102-108.
(5) Barton, P. (1991). Piriformis syndrome: a rational approach to management.
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