Ischial bursitis

Ischial bursitis also known as “ischiogluteal bursitis” or “weaver’s bottom,” is a rare condition where the bursa that lies between the ischial tuberosity and the gluteus maximus muscle becomes inflamed ¹, ². Bursitis is the swelling and irritation of a bursa. A bursa is a small fluid-filled sac that acts as a cushion between muscles, tendons, and bones ³. Bursa is located throughout the body, including around the shoulder, elbow, hip, knee, and heel. Ischial bursa is present physiologically in order to reduce the amount of frictional force generated between the gluteal muscle and the ischial tuberosity that otherwise might become damaged or irritated by this contact ⁴. Ischial bursitis is most commonly caused by prolonged pressure on the ischium, as occurs in prolonged sitting or from the repeated movement of the gluteus maximus muscle in such activities as bicycling or running ⁵, ⁶. Ischial bursitis or ischiogluteal bursitis has been known to be common in people whose occupations are related with frequent irritation to the bursa, and this irritation can occur during long periods of time spent in the sitting position ⁷. When vibration is involved in working, such as with heavy powered sewing machine (weavers), tractor-driving or road equipment machines, the ischiogluteal bursa can become inflamed ⁸, ⁹. Furthermore, as the ischial tuberosity bears the weight of the body in the supine position (laying on your back), these pressure points may lead to ischial bursitis in debilitated persons, and particularly for those patients with malignancies or paraplegia ¹⁰, ¹¹. Ischial bursitis can also be affected by an acute or chronic shearing force on the ischial tuberosity caused by falling on your backsides (buttocks) in athletes, resulting in chronic and sometimes disabling discomfort that can prevent athletes from participating in their sporting activities ¹². There are many sports that involve sitting such as canoeing, horseback riding, wheel-chair racing for paraplegic patients and so on ⁷. These activities cause an inflammatory reaction that results in swelling and tenderness over the lower buttock and upper posterior thigh. Many other differential diagnoses have common presentations such as sciatica, lumbar disc degeneration, piriformis syndrome, sacroiliitis, hip bursitis and tendonitis of hamstring muscles ¹³, ¹⁴, ¹⁵.

Ischial bursitis symptoms may include mass-like sensation along the buttock, or as buttock pain radiating down the lower leg ¹⁶. Patients with ischiogluteal bursitis often complain of mild-to-moderate pain in the buttocks with occasional pain radiating down the gluteal/thigh area, often worsening with prolonged sitting or exercise. Forward bending of the hip joint or standing on the tiptoes can exacerbate pain ¹⁷. Physical examinations showed the tenderness of ischial tuberosity area in 59 (92.2%) patients, but no specific findings were confirmed in 5 patients (7.8%) ¹⁸. As the ischiogluteal bursa lies in a close contact with the sciatic and posterior femoral cutaneous nerves, ischial bursitis can mimic the symptoms of radiculopathy ¹⁸, ¹⁹. Enlargement of ischiogluteal bursa could clinically mimic a soft tissue neoplasm ²⁰, ²¹, ²².

The ischiogluteal bursa is an adventitial bursa located between the ischial tuberosity and the gluteus maximus muscle, smoothing movement by reducing friction between the two ⁸, ²³. An adventitial bursa is a non-native structure which develops later in life through a process of myxoid degeneration of fibrous tissue secondary to abnormal stress and friction between adjacent structures ²². Adventitial bursa does not have lining cells ²². Ischial bursa is synovial, meaning it is composed of a fatty connective tissue capsule filled with synovial fluid ⁸, ²⁴. When infection or irritation occurs, cells of the synovia proliferate, resulting in increased production of synovial fluid. Inflammatory mediators such as cyclooxygenase, cytokines, and metalloproteases mediate this process. The result is a thick fluid-filled cavity with high amounts of fibrin, resulting in the formation of granulation tissue ²⁵. Over time, this tissue will gradually interfere with the normal motion and activity of the surrounding tissues whether they are muscle, bone, or tendon.

Ischial bursitis is a relatively uncommon clinical condition nowadays, and it is often overlooked as a cause of buttock pain ¹⁵, ⁹. Ischial bursitis is often diagnosed after exclusion of other causes of pain at the buttock ²⁶, ¹⁸. In addition, the symptoms of ischial bursitis are varied and often non-specific, making it difficult to diagnose and confused with many other diseases ¹⁸. Moreover, it is difficult to predict cases of chronic progression or poor treatment response.

Although there are no specific radiographic findings that are diagnostic of ischiogluteal bursitis, the most common findings in a long-standing ischiogluteal bursitis would be irregularity of the cortex of the ipsilateral ischial tuberosity, or any calcification projecting over or near the tuberosity ¹⁵, ²⁷. Prior imaging should be reviewed to identify other potential causes of pain in this region such as referred pain, calcium hydroxyapatite deposition, or other masses including myxoid tumor, schwannoma, or neurofibroma ⁶. Although the diagnosis is often unrecognized, it may be seen in patients of all ages. Bursitis as whole accounts for less than one percent of total primary care visits. Ischial bursitis is most common in persons with sedentary careers with constant irritation of the ischial bursa due to prolonged periods of time sitting on hard surfaces which gives this condition it’s colloquial name “weaver’s bottom.” Weaving as a profession has been around since approximately 6000 BCE, and people have been suffering from this condition for as many years ²⁸.

Most previous studies reported on conservative treatment of ischiogluteal bursitis, including administration of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen, aspiration, and bursal injection of steroids or local analgesics ¹⁸, ². Among these treatments, lifestyle modification and avoidance of triggering activities was found to be the most fundamental treatment ²⁷. It is important to educate the patient on lifestyle changes including weight loss and regular exercise. Recurrences are common in patients who lead a sedentary lifestyle ²⁹.

Cold compresses may help in the short term to minimize pain from swelling. In most cases, a satisfactory response is obtained from conservative treatment, with the expectation of a favorable prognosis thereafter; however, improvement of symptoms is slow in some cases, showing chronic progression ¹⁸. If the pain is unbearable or unrelenting, an intrabursal corticosteroid injection with lidocaine may be administered ³⁰, ³¹, ³². The lidocaine will help by providing immediate relief from the pain by blocking the sodium channels in the surrounding tissue, inhibiting the transmission of the pain signal ³³.

Surgical treatment should be considered in cases of refractory ischiogluteal bursitis, and in this study, encouraging results were obtained after performance of surgical excision in all cases ³⁴.

Figure 1. Ischial bursitis

Figure 2. Ischial bursitis ultrasound

Footnote: Ischiogluteal bursitis ultra-sonography in a 76-year female shows hypoechoic lesion (yellow arrows) with acoustic enhancement.

[Source  ¹⁸ ]

Figure 3. Ischial bursitis MRI

Footnote: Ischial bursitis MRI findings. (A) Rotated axial T2 fat-saturated and (B) T1 fat-saturated post contrast MRI images demonstrate a rim enhancing fluid collection adjacent to the ischial tuberosity within the ischial bursa.

[Source ²⁶ ]

Ischial bursitis causes

The origin of ischial bursitis can be seen in the original name of the condition, “weaver’s bottom” ³⁵. Ischial bursitis was first seen in workers that sat for long periods of time on hard surfaces. Another colloquial name for this condition is “tailor’s bottom.” Ischial bursitis may occur in various conditions, much like many other bursal inflammations. Although chronic microtrauma from chronic repetitive friction on the tissue overlying the bursa around the ischial tuberosity, the cause of ischial bursitis remains unclear ³⁶, ³⁷, ³⁸. Roh et al. ¹⁸ reported that inflammatory disease is an independent risk factor for refractory ischiogluteal bursitis. Involvement of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus (SLE), and scleroderma among others, are also likely to cause ischiogluteal bursitis; however, few studies have been reported thus far ³⁹.

Ischial bursitis may also be caused by uremia seen in conditions such as gout and chronic kidney disease ¹⁸. Ischial bursa is a deep bursa, meaning it is less susceptible to the contiguous spread of infectious organisms. Although rare, infectious etiologies of ischial bursitis include septicemia and septic arthritis ⁴⁰. Direct inoculation of the bursa by bacteria would be very rare due to its location in the body ³⁵.

Ischial bursitis symptoms

Patients with ischial bursitis will present with gluteal pain and/or upper posterior thigh pain following prolonged sitting or exercise ². The patient will most commonly complain of a low grade, pinpoint, aching pain that is worsened by sitting down or stretching the gluteus maximus muscle ⁴¹. Patients may complain of problems sleeping because of the pain. Patients also may have reduced mobility and swelling associated with this condition. On physical exam, tenderness over the buttock may be noted. Patients may have pain with passive flexion at the hip joint ². The patient also may have an inability to extend the hip ⁴¹. The patient may feel pain with stretching ⁴². A soft tissue mass, which tends to be well-defined, non-mobile, and slightly tender, may be present in the gluteal region of the affected hip ⁴³. When redness (erythema) overlying the gluteal regions is a major clinical presentation, infectious causes such as cellulitis or septic joint should be suspected ¹⁸. In a study by Roh et al ¹⁸, tenderness on ischial tuberosity was positive in 59 patients (92.2%) during a physical examination, while no specific findings were confirmed in the 5 patients (7.8%). Therefore, even if there is no tenderness of ischial tuberosity in physical examination, ischial bursitis should not be completely excluded ¹⁸.

Ischial bursitis complications

Ischial bursitis can result in problems with ²:

• Walking
• Running
• Sitting
• Stretching

Subsequent avoidance of activity and exercise may lead to overall poor conditioning and negatively affect other conditions that respond well to or are prevented at some level by exercise and activity.

Ischial bursitis diagnosis

Most ischial bursitis cases can be diagnosed and treated clinically without the need for further testing ². Most cases of ischial bursitis are self-limiting and will resolve with time. Blood work should only be ordered if an infection or autoimmune condition is suspected. In the case of bursitis, lab values will most likely be within normal range. If other conditions are suspected, such as septic joint, a joint aspiration is indicated, and antibiotic treatment should be initiated.

Radiological evaluation is helpful when the clinical diagnosis is obscured for patients having buttock pain and/or a mass ⁷. When imaging is indicated for the diagnosis, MRI and/or ultrasound is the first choice of modality ⁷. There are at least two advantages for using MRI in this situation. The first is that MRI is sensitive for bursitis and MRI provides a global view for finding causative lesions of buttock pain or a mass in the pelvis, hip, and soft tissue, or for excluding the possibility of spinal diseases ⁷. The second is that the T2-weighted MRI images clearly identify and localize the inflamed bursa according to the characteristic MRI findings of bursitis at the expected location ¹². However, MRI is expensive and unnecessary most of the time when diagnosing and treating ischial bursitis. MRI is only indicated if there are other possible differentials such as tumors. Ultrasound, similarly, is unnecessary unless aspiration is indicated, then it is useful to guide the procedure ensuring aspiration is performed in the appropriate place ⁴⁴.

It is important to differentiate ischiogluteal bursitis from peri-rectal or buttock abscess, hematoma, epidermoid cyst, dermoid cyst or hydatid cyst when the lesion shows a cystic appearance ⁷. The typical location of ischiogluteal bursitis might be a very important diagnostic criterion for separating bursitis from the other cystic masses ⁷. The common hamstring tendon is typically located lateral to the inflamed ischiogluteal bursa, and it possibly acts as a barrier to prevent the extension of the bursitis ⁷. Instead, the enlarged bursa usually spreads inferomedially to the ischiorectal fossa ⁷.

Ischial bursitis or ischiogluteal bursitis, when it occurs in cancer patients, it may clinically mimic a soft-tissue or bone metastasis from the primary malignancy ¹⁰, ⁴⁵. Whenever the possibility of tumor is in the differential diagnosis, biopsy or surgical intervention should be performed for confirmation ⁷. In addition, an enlarged bursa should be aspirated to exclude an infectious process whenever this is suspected ⁷.

Tuberculosis, gout, rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis and Reiter’s syndrome have also been reported to involve the ischiogluteal bursa ⁷, ⁴⁶, ⁴⁷, ⁴⁸, ⁴⁹, ⁴⁵, ⁹, ⁵⁰.

Ischial bursitis treatment

Initially, the common nature of ischial bursitis should indicate minor, low-cost interventions such as nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen and rest ². If ischial bursitis persists, therapeutic mixed steroid and anesthetic injections may be considered ². Only if the condition continues to be resistant or other causes are indicated by the workup for this patient presentation should more invasive and/or expensive test be used.

Treatment of ischial bursitis is relatively symptom driven ². Primary treatment is lifestyle modification by stopping the activity that caused bursitis in the first place, whether it was a physical activity or sitting for long periods of time on hard surfaces. Nonsteroidal anti-inflammatory drugs such as naproxen work well to decrease inflammation, and a regiment of daily intake for two weeks may be followed to prevent further inflammation. Naproxen also may help reduce pain associated with this condition. Cold compresses may help in the short term to minimize pain from swelling.

The rate of recovery is highly depending on the severity of patient symptoms and modality of treatment chosen. Recurrence is likely without lifestyle change ³⁵.

Ischial bursitis injection

If the pain is unbearable or unrelenting, an intrabursal corticosteroid injection with lidocaine may be administered (Table 1) ². The lidocaine will help by providing immediate relief from the pain by blocking the sodium channels in the surrounding tissue, inhibiting the transmission of the pain signal ². The corticosteroid will provide prolonged anti-inflammatory protection by inhibiting the inflammatory mediators. Patients will most likely be symptom-free within days to weeks without treatment ⁵¹.

While injectable steroids are frequently used to treat pain, there is no consensus regarding the superiority of a specific agent, for bursal injections ²⁶. Commonly used steroids, however, do contain slightly different properties. For example, particulate steroids such as methylprednisone, triamcinolone and betamethasone have lower solubility and therefore, theoretically last longer at the injection site compared to non-particulates such as dexamethasone ²⁶.

Injection of the ischial bursa is typically performed with the patient in the prone position ²⁶. The ultrasound probe is then used to identify the hamstring muscles which are followed superiorly to the ischial tuberosity while noting the location of the sciatic nerve ²⁶. The transducer is placed in the transverse plane over the most lateral aspect of the ischial tuberosity, and the needle is directed towards the space between the ischial tuberosity and gluteus maximus. Once the needle is at the peri-bursal fat, a mixture of 40 mg of triamcinolone or methylprednisolone and 4 mL of lidocaine is then injected into the bursa ²⁶. Although steps are taken to avoid major neurovascular structures, it is still possible for some of the injectate to reach the sciatic nerve. Therefore, the use of shorter acting anesthetics is preferred, and patients are instructed to avoid operating a vehicle immediately following the appointment ²⁶.

Side effects are usually mild and may include facial flushing, skin reaction/hypopigmentation, soft tissue atrophy, steroid flare, transient increase in blood sugar ⁵², ⁵³, adverse psychiatric effects ⁵⁴, ⁵⁵ and allergic reaction ranging from mild to anaphylaxis. Allergy to injectable steroids is rare and may be related to a medication additive rather than the steroid itself ⁵⁶. For extra-articular steroid injections, major adverse events have been reported as occurring 0–5.8% with minor adverse events ranging from 0 to 81% ⁵⁷. Pain following injection is the most common minor adverse event ⁵⁷, described as a transient issue, not requiring intervention. Infection is an extremely rare complication, with an incidence rate of 0.0046% ⁵⁸.

Table 1. Commonly used injectable steroids and local anesthetics

Steroids	Anesthetics
Methylprednisolone acetate (40 mg/mL or 80 mg/mL)	Lidocaine (1%)
Triamcinolone acetonide (40 mg/mL)	Bupivacaine (0.25%)
Betamethasone acetate (6 mg/mL)	Ropivacaine (0.5%)
Dexamethasone sodium phosphate (4 mg/mL)

[Source ²⁶ ]

Surgical treatment

Surgical treatment is recommended in patients with persistent or repeated superficial bursitis and significant enlargement of bursa causing functional disability ¹⁸. Surgical treatment includes open or endoscopic bursectomy and partial excision of the underlying bony tissue ¹⁸.

Ischial bursitis prognosis

Unless the underlying inflammatory diseases that cause of ischial bursitis is accurately identified and addressed, ischial bursitis will usually not spontaneously recover ². The pain may abate with a period of lay-off or treatment, but reinitiating activity will still lead to excessive friction on the ischio-gluteal bursa, causing inflammation and the recurrence of pain ². Patients with underlying inflammatory diseases, such as rheumatoid arthritis, gout, and skin infection, showed less responsiveness to conservative management, and two of the patients in this study required open surgical intervention due to failure of medical treatment ¹⁸, ⁵⁹.

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