Ischial Bursitis

Etiology

Originally named "weaver's or tailor's bottom," inflammation of the ischial bursa can result from extended periods of sitting on hard surfaces.[1] Factors associated with the development of ischial bursitis include occupation, history of trauma, sedentary lifestyle, duration of sitting, and obesity.[8] Although various clinical manifestations have been reported, prolonged pressure on the ischium, particularly during sitting, remains the predominant cause.[3] 

Ischial bursitis frequently affects individuals with a sedentary lifestyle.[1]. Professions involved with heavy vibration also have implications for developing ischial bursitis, such as using heavy-powered sewing machines, road equipment, or driving tractors. Repeated exposure to body vibration, while seated on a hard surface, can provoke irritation and inflammation of the ischiogluteal bursa, leading to bursitis.[9]

Another etiology involves the application of acute or chronic shearing force after a fall involving the ischial tuberosity, such as landing on the backside. This mechanism can also affect athletes who frequently experience "falls" onto the ischial tuberosity, such as horseback riders, canoeists, and wheelchair racers.[9] Additionally, even in the supine position, significant weight can be placed on the ischial tuberosity, leading to documented cases of ischial ulcers and bursitis in debilitated patients.[8][9]

Autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, and scleroderma, are recognized causes of bursitis.[2] Patients with underlying inflammatory conditions such as gout, rheumatoid arthritis, and skin infections who develop ischial bursitis often exhibit reduced responsiveness to conservative management.[8]

Infectious and hemorrhagic bursitis primarily affects superficial bursae and is less commonly associated with deep bursitis, such as ischiogluteal bursitis. However, the proximity of the ischial bursa to the anus and urethra increases the potential for bacterial infection, especially if there is damage to the overlying skin in that area.[1][10]

Epidemiology

The incidence and prevalence of ischial bursitis are unknown, with no recent data available on this subject. While bursitis, in general, is reported equally in males and females and across all age groups, ischial bursitis is comparatively rarer and less frequently recognized.[1][11]

A retrospective study conducted in 2020 on the progression and treatment of ischial bursitis revealed no discernible difference in responsiveness to treatment based on gender, age, body mass index, occupation, trauma history, affected side, sitting lifestyle, sitting time, erythrocyte sedimentation rate (ESR), C-reactive protein, or uric acid levels. However, the presence of inflammatory disease significantly differed between the 2 groups with different treatment responsiveness. In addition, the study found a higher prevalence of ischial bursitis among individuals with sedentary jobs compared to those engaged in physically demanding labor. Interestingly, occurrences were also reported among patients who reported non-working status.[1]

Pathophysiology

Repetitive, chronic, and sustained injury to the bursa leads to local vasodilation and increased vascular permeability, allowing serum protein and fluid to exit the vessels and accumulate within the bursa's fluid. This material stimulates inflammatory processes, resulting in enlarged and painful bursae.[1][10] This process is particularly prominent in patients with autoimmune or inflammatory diseases such as rheumatoid arthritis, syphilis, hypothyroidism, systemic scleroderma, and spondyloarthropathies.[10]

Another possible presentation of ischial bursitis involves sharp, shooting radicular pain that travels down the back of the lower extremity. When an enlarged bursa extends to compress the sciatic nerve as it exits the sciatic foramen and progresses down the posterior leg, it can induce the characteristic presentation of sciatica. Additionally, compression of the nearby posterior femoral cutaneous nerve by the bursa may lead to referred pain in the posterior medial thigh, extending as far as the popliteal fossa or medial buttock.[9]

Crystal deposition can also cause bursitis, particularly associated with conditions such as rheumatoid arthritis, gout, pseudogout, and spondyloarthropathies. The abnormal deposition of materials into the bursa is usually a response to a chronic inflammatory state.[1][10]

History and Physical

Understanding the historical context and performing a comprehensive physical examination are crucial aspects in evaluating patients suspected of ischial bursitis. Clinicians can discern key clinical clues and anatomical features essential for accurate diagnosis and effective management of this condition.

Clinical History

The most common initial presentation of ischial bursitis is buttock pain, characterized as a low-grade, pinpoint, aching sensation exacerbated by sitting or stretching the gluteus maximus.[12][13][14] Additional reported symptoms among patients include radiating upper posterior thigh pain following prolonged sitting or exercise, inguinal, trouble sleeping and reduced hip mobility secondary to pain, difficulty rising from a seated position or climbing stairs, and swelling around the ischial tuberosity.[1][2][12] 

Patients often report pain during passive hip flexion and experience challenges with hip extension.[4] In addition, the proximity of the hamstring tendon attachment on the ischial tuberosity can cause exacerbation of pain during knee flexion.[12] Some patients may also describe shooting pain down the back of the affected leg and posterior thigh pain.[3][9][13] Pain usually improves with rest, alterations in activities of daily living, and nonsteroidal anti-inflammatory drugs (NSAIDs).[12]

Physical Examination

The most notable finding on physical examination is tenderness over the buttock, which is most prominent when the patient's hip is flexed and the ischial tuberosity is palpable.[1][14] Other potential physical findings include positive results on specific tests, including straight leg raise, flexion-adduction-internal rotation (FADIR), and Faber (Patrick).[1] In some cases, a soft, well-defined, nonmobile, and slightly tender mass may be palpable in the gluteal region.[1][15] Larger lesions may exhibit pigmented skin around the affected site.[3] However, even in the absence of tenderness of the ischial tuberosity, ischial bursitis should not be ruled out, as some patients with confirmed ischial bursitis present with no specific findings on physical examination.[1]

Evaluation

While the clinical diagnosis of ischial bursitis based on history and physical examination is adequate for some patients, those with more intricate presentations often benefit from imaging studies to confirm the diagnosis. The standard practice involves conducting an ultrasound initially, followed by magnetic resonance imaging (MRI) if the diagnosis remains ambiguous.[1][2] Radiographs are typically unremarkable except in calcifying ischial bursitis.[15][16]

Ultrasound

Ultrasound findings of ischial bursitis can vary. The bursal wall often exhibits a hypoechoic appearance, although it may appear hyperechoic in certain patients. Similarly, the bursal fluid typically appears hypoechoic but can also be hyperechoic or heterogeneous. Any internal septa or mural nodules present usually appear hyperechoic. The probe is expected to compress all bursae during an ultrasound examination for optimal visualization.[16]

Magnetic Resonance Imaging

MRI of ischial bursitis typically reveals a fluid-filled and distended bursa, with concurrent abnormalities in the nearby hamstring muscle complex being common. Bursitis findings include well-defined, lobulated septate lesions with a thin bursa and increased fluid intensity signals.[1][2][3] However, lesion enhancement on MRI can vary. MRI of ischial bursitis with T1-weighted images typically shows low-to-intermediate signal intensity, with some patients demonstrating peripheral ring-like intensity findings. T2-weighted images usually display high signal intensity, with variations in bursa homogeneity.[1][15] In addition, wavy contours with increased fluid signal intensities demonstrate hamstring muscle complex abnormalities, indicating chronic microtearing of tendons.[1]

Aspiration

In cases of suspected infection, aspiration of the ischial bursa may be required. Additional evaluation for suspected infection in patients with ischial bursitis should involve laboratory studies, notably a complete blood count and an ESR. If infection is confirmed, the infected bursa should be drained and cultured, followed by appropriate antibiotic therapy.[10]

Treatment / Management

Conservative therapy proves effective in most individuals with ischial bursitis. NSAIDs, lifestyle modifications, pressure-relieving pillows, and physical therapy, including extracorporeal shock wave therapy, have demonstrated efficacy in providing relief without the necessity of intrabursal injections for many patients.[1][12] Primary treatment focuses on lifestyle modifications aimed at avoiding activities or habits that initially provoked the pain. Extracorporeal shock wave therapy aids in reducing adhesions in chronic bursitis by breaking down scar tissue and restoring the normal orientation of collagen fibers, thereby enhancing mobility and alleviating pain.[1][10][12] Other conservative measures include cold therapy, rest, stretching exercises, and fractional massage.[2](B2)

Intrabursal injections with corticosteroids and local anesthetics are also effective for patients who experience unbearable and unrelenting pain and require further treatment.[4][14][17] Some patients with nonresponsive ischial bursitis have found relief after surgical excision of the bursa.[1][10] The inflamed tissue surrounding the bursa can also be cleared through open or laparoscopic bursectomy.[13](B2)

Differential Diagnosis

When ischial bursitis is considered part of a differential diagnosis and local injection with anesthetic and/or corticosteroids provides only temporary relief, it is essential to explore other potential diagnoses.[11] Alternative causes of pain in the region of the ischial bursa and gluteal muscles include sciatica, lumbar disc degeneration, piriformis syndrome, greater trochanteric bursitis, coccydynia, sacroiliitis, and local nerve impingement.[1][9][11]

When manifestations of ischial bursitis involve a soft, nonmobile mass in the buttock, investigation for potential neoplastic conditions may be warranted, with MRI being the preferred imaging modality. Neoplastic lesions typically exhibit solid soft tissue components, whereas bursitis presents as cystic with a localized fluid collection and a thin wall.[15]

Another potential source of pain that may be misattributed to irritation of the ischial bursa is hamstring tendinopathies. The hamstring muscle complex plays a crucial role as the primary active extensor of the pelvis and flexor of the knee, rendering it highly prone to sprain and injury. Given the proximity of the conjoined tendon and semitendinosus tendons to the ischial bursa at their origins on the ischial tuberosity, distinguishing the cause of point tenderness at that site can be challenging.[2] 

Similar findings between the diagnoses include point tenderness often elicited at the ischial tuberosity, pain in the buttock or posterior thigh, discomfort when rising from a seated position, and local swelling in the affected area, depending on the severity of the bursitis. Ischial bursitis can also be concurrent with hamstring muscle complex tendinopathy and may be identified through appropriate imaging techniques.[7][17]

Prognosis

The time required to achieve symptomatic relief from ischial bursitis differs among treatment modalities and can vary from days to weeks. Conservative approaches, such as lifestyle modifications and NSAIDs, may take longer to yield relief, influenced by factors such as patient adherence, pain severity, and the ability to alleviate pressure from the ischial tuberosity. On the other hand, corticosteroid and anesthetic injections usually start providing relief within minutes to days. Notably, informing patients that their pain might take several days to subside is important.[14]

Patients with underlying inflammatory disease have shown less responsiveness to conservative measures and may necessitate more aggressive interventions for pain relief. This consideration holds significance in treatment response and patient education.[1] Ischial bursitis is recognized for its high recurrence rate and tendency for chronic progression, often entailing slow recovery. The high recurrence rate suggests that invasive treatment can occasionally be indicated after establishing refractory cases.[14]

Complications

While ischial bursitis itself is not typically associated with severe complications, untreated or recurrent cases can lead to chronic pain and functional limitations. Prolonged inflammation of the ischial bursa may result in fibrosis or calcification, further exacerbating discomfort and reducing mobility. Additionally, persistent bursitis can contribute to secondary complications such as muscle weakness, altered gait mechanics, and decreased quality of life.

In rare cases, severe and untreated ischial bursitis may lead to secondary infections or abscess formation within the bursa, requiring prompt medical intervention. Septicemia and septic arthritis are infrequent due to the bursa's deep location. Previous studies have not conclusively established a relationship between these complications and ischial bursitis.[1] Nevertheless, early recognition and appropriate management of ischial bursitis are crucial to mitigate potential complications and optimize patient outcomes.