Psoas Bursitis

Psoas Bursitis

Psoas bursitis is an uncommon cause of hip and groin pain that is frequently misdiagnosed in clinical practice. A patient with psoas bursitis frequently reports pain in the groin. The pain is localized to the area just below the crease of the groin anteriorly, with referred pain noted into the hip joint. Often, the patient is unable to sleep on the affected hip and may report a sharp, catching sensation with range of motion of the hip.

The psoas muscle flexes the thigh on the trunk or, if the thigh is fixed, flexes the trunk on the thigh as when moving from a supine to a sitting position. This action can irritate the psoas bursa, as can repeated trauma from repetitive activity, including running up stairs or overuse of exercise equipment for lower extremity strengthening.

The psoas muscle is innervated by the lumbar plexus. The psoas bursa lies medially in the femoral triangle between the psoas tendon and the anterior aspect of the neck of the femur. This bursa may exist as a single bursal sac or in some patients may exist as a multisegmented series of sacs that may be loculated in nature. The psoas bursa is vulnerable to injury from acute trauma and repeated microtrauma. Acute injuries frequently take the form of direct trauma to the bursa from seat belt injuries and from overuse injuries requiring repeated hip flexion, such as javelin throwing and ballet. If the inflammation of the psoas bursa becomes chronic, calcification of the bursa may occur.

What are the Symptoms of Psoas Bursitis

Physical examination may reveal point tenderness in the upper thigh just below the crease of the groin in patients with psoas bursitis.

Passive flexion, adduction, and abduction and active resisted flexion and adduction of the affected lower extremity reproduce the pain. Sudden release of resistance during this maneuver markedly increases the pain. Examination of the hip is normal, unless there is coexistent internal derangement of the hip.

How is Psoas Bursitis diagnosed?

Plain radiographs of the hip may reveal calcification of the bursa and associated structures consistent with chronic inflammation. Magnetic resonance imaging (MRI) and ultrasound imaging is indicated if occult mass, abscess, or tumor of the hip or groin is suspected.

Complete blood cell count and automated chemistry profile, including uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, are indicated if collagen-vascular disease is suspected. Injection of the psoas bursa with a local anesthetic and steroid serves as a diagnostic maneuver and a therapeutic maneuver.

Differential Diagnosis

Psoas bursitis is often misdiagnosed as an inguinal hernia or attributed to a primary hip pathological process. Radiographs of the hip and electromyography help distinguish psoas bursitis from radiculopathy of pain emanating from the hip. Most patients with lumbar radiculopathy have back pain associated with reflex, motor, and sensory changes, whereas patients with psoas bursitis have only secondary back pain as a result of altered gait and no neurological changes.

Femoral diabetic neuropathy sometimes may be confused with psoas bursitis, but can be distinguished by the presence of motor and sensory changes involving the femoral nerve.

These motor and sensory changes are limited to the distribution of the femoral nerve below the inguinal ligament. Ilioinguinal and genitofemoral neuropathy also can be confused with psoas bursitis. Lumbar radiculopathy and these nerve entrapments may coexist as the “double crush” syndrome.

The pain of psoas bursitis also may cause alteration of gait, which may result in secondary back and radicular symptoms that may coexist with this entrapment neuropathy.

Treatment

Initial treatment of the pain and functional disability associated with psoas bursitis should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold also may be beneficial.

The repetitive movements that incite the syndrome should be avoided. For patients who do not respond to these treatment modalities, injection of the psoas bursa with a local anesthetic and steroid may be a reasonable next step. Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.

Complications and Pitfalls

The proximity to the femoral nerve of the psoas bursa makes it imperative that the injection procedure be done only by clinicians well versed in the regional anatomy and experienced in performing injection techniques.

Many patients report a transient increase in pain after injection of the bursa.

Clinical Pearls

It is important to rule out other causes of groin pain, including inguinal hernia and entrapment neuropathies of the ilioinguinal, genitofemoral, and femoral nerves. Injection of the psoas bursa is extremely effective in the treatment of psoas bursitis. Special care must be taken to avoid trauma to the femoral nerve.

The use of physical modalities, including local heat and gentle stretching exercises, should be introduced several days after the patient undergoes this injection technique.

Vigorous exercises should be avoided because they would exacerbate the symptoms. Simple analgesics, NSAIDs, and antimyotonic agents such as tizanidine may be used concurrently with injection of the bursa.

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