Clunealgia is an uncommon cause of inferior buttock pain that is frequently misdiagnosed as primary hip pathological conditions or gluteal or ischial bursitis. A patient with clunealgia frequently reports pain in the inferior gluteal region that is made worse by prolonged sitting.
Paresthesias in the distribution of the inferior cluneal nerves may also be present. Pain may be referred to the groin, perineum, and genitals. Often, the patient is unable to sleep on the affected side and may report a sharp, catching sensation and paresthesias when first awakening.
Providing innervation to the inferior buttocks, the inferior cluneal nerves are terminal branches of the posterior femoral cutaneous nerve. Both the posterior femoral cutaneous nerve and the inferior cluneal nerves are subject to stretch injury and to compression by aberrant muscles, particularly the piriformis, abnormal masses, hematomas, and tumors.
What are the Symptoms o
Physical examination of patients with clunealgia may reveal tenderness to palpation of the inferior buttocks. Deep palpation at the inferiolateral margin of the ischial tuberosity my reproduce the patient’s pain symptomatology and on occasion elicit paresthesias into the perineum, groin, and genitals. Examination of the hip and sacroiliac joint should be normal. Careful neurological examination of the affected lower extremity should reveal no neurological deficits. If neurological deficits are present, evaluation for plexopathy, radiculopathy, or entrapment neuropathy should be undertaken. These neurological symptoms can coexist with clunealgia, confusing the clinical diagnosis.
How is Clunealgia diagnosed?
Pelvic, scrotal, testicular, and rectal examination are indicated in all patients suspected of suffering from clunealgia. Plain radiographs and computed tomography of the hip and pelvis are indicated to rule out occult hip and pelvic bony pathology. Magnetic resonance imaging (MRI) and ultrasound imaging is indicated to identify occult mass or tumors that may be compressing the posterior femoral cutaneous nerve and its branches and if tumor of the hip or tear of the gluteal muscles is suspected. Electromyography should be performed if neurological findings are present to rule out plexopathy, radiculopathy, or nerve entrapment syndromes of the lower extremity. Based on the patient’s clinical presentation, additional tests, including complete blood cell count; human leukocyte antigen (HLA) B-27 testing; automated serum chemistries, including uric acid; erythrocyte sedimentation rate; and antinuclear antibody testing, may be indicated. Injection of the inferior cluneal nerves can be utilized as a diagnostic and therapeutic maneuver. A positive diagnostic block of the inferior cluneal nerves at the inferiolateral margin of the ischial tuberosity strengthens the diagnosis of clunealgia.
Clunealgia is often misdiagnosed as ischial or gluteal bursitis or the patient’s symptoms attributed to primary hip pathological processes.
Radiographs and ultrasound imaging of the hip and electromyography help distinguish clunealgia from radiculopathy, sciatica, or pain emanating from the hip.
Most patients with a lumbar radiculopathy have back pain associated with lower extremity reflex, motor, and sensory changes, whereas patients with clunealgia will demonstrate neurological deficits that are limited to the distribution of the inferior cluneal nerves. Piriformis syndrome sometimes may be confused with clunealgia but can be distinguished by the presence of motor and sensory changes involving the sciatic nerve. These motor and sensory changes are limited to the distribution of the sciatic nerve below the sciatic notch.
Lumbar radiculopathy and sciatic nerve entrapment may coexist as the “double crush” syndrome. It should be noted that in some patients, there is significant overlap of the sensory distribution of the pudendal and inferior cluneal nerves.
Initial treatment of the pain and functional disability associated with clunealgia should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold may be beneficial.
Any repetitive movements including sitting for prolonged periods that incite the syndrome should be avoided. For patients who do not respond to these treatment modalities, injection of inferior cluneal nerves with a local anesthetic and steroid may be a reasonable next step as both a diagnostic and therapeutic maneuver.
Ultrasound, computed tomography, or magnetic resonance imaging guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications
The proximity of the inferior cluneal nerve to adjacent structures makes it imperative that this procedure be performed only by clinicians well versed in the regional anatomy and experienced in performing injection techniques. A failure to identify the pathology responsible for compromise of the inferior cluneal nerves can lead to disastrous results.
This injection technique is extremely effective in the treatment of clunealgia. It is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected.
Care must be taken to use sterile technique to avoid infection and universal precautions to avoid risk to the operator.
Most side effects of this injection technique are related to needle-induced trauma to the injection site and underlying tissues. Ultrasound guidance may help decrease needle-related complications.
The incidence of ecchymosis and hematoma formation can be decreased if pressure is placed on the injection site immediately after injection. The avoidance of overly long needles helps decrease the incidence of trauma to underlying structures. Special care must be taken to avoid trauma to the sciatic 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. Simple analgesics, NSAIDs, and tricyclic antidepressants to help with sleep disturbance may be used concurrently with this injection technique.