A bursa is a sac-like, fluid-containing structure that is part of the musculoskeletal system. Bursae are located where friction occurs (between bony prominences or near tendons, muscles, and other soft tissues that abut bony structures); they serve as cushions to reduce the mechanical stresses of movement.
Bursae can be found in the shoulder; between the shoulder blade and the ribs; around the elbow, knee, big toe, or heel; overlying the ischial tuberosities (the bones that bear weight during sitting); over the greater trochanter (point of the hip); and elsewhere.
When an inflammatory process occurs within a bursa – a condition known as bursitis – it can become swollen, red, warm, and painful. Bursitis near a joint can mimic arthritis. (Ensworth S. Rheumatology: 1. Is it arthritis? CMAJ 2000;162:1011-6)
Causes of Bursitis
Bursae are lined with the same synovial membrane that lines joints; indeed, some bursae are directly attached to and communicate with nearby joints. Thus, bursae are subject to the same inflammatory processes that affect joints.
Bursitis may be caused by, or associated with:
- Inflammatory arthritis (rheumatoid, psoriatic, lupus, etc.)
- Crystal-induced arthritis (e.g., gout or pseudogout)
- Overuse, either acute or chronic
- Direct injury to the bursa
- Infection
- Hemorrhage (bleeding into a bursa – often due to direct trauma – causes irritation of the bursal lining)
Bursitis can be either acute or chronic. In the latter, the walls and inner lining of the bursal sac become thickened and roughened. Calcium deposits may form within the bursa, and adhesions (scarring) may form.
(Adapted from Bursitis, Tendinitis, and Fibromyalgia in The Merck Manual, 18th Edition. 2006:319-20)
Signs and Symptoms of Bursitis
Acute bursitis, whatever the cause, usually produces pain that worsens with motion of the structures surrounding the bursa. The bursa is often tender to touch or pressure.
Other signs and symptoms include:
- Swelling, particularly if the bursa lies close to the skin
- Redness (more common in crystal-induced bursitis or infection)
- Warmth of the skin overlying the bursa
- Reduced joint motion (more common in chronic bursitis, in particularly painful forms of acute bursitis [e.g., infectious], and in cases where a bursa communicates directly with a joint)
Diagnosis of Bursitis
Diagnosis of bursitis is usually unambiguous. Persons who develop pain, swelling, or warmth over bursae usually have bursitis.
Whenever the diagnosis is in question – if extraordinary pain, redness, fever, or other signs raise suspicions of unusual underlying pathology – additional tests may be necessary to clarify the diagnosis:
- X-ray
- Bursal aspiration (fluid is withdrawn from the bursa following administration of a local anesthetic; the fluid is analyzed for bacteria, crystals, etc.)
- Blood tests (blood count, erythrocyte sedimentation rate, uric acid level, lupus panel, etc.)
Treatment of Bursitis
Most cases of bursitis are due to overuse syndromes (e.g., unusually intense or prolonged exercise). In acute cases of overuse, treatment should consist of: temporary rest; splinting; anti-inflammatory medications; intermittent applications of heat and ice; and, as pain subsides, physical therapy and graded exercise usually address the problem.
When acute bursitis persists, it is sometimes helpful to remove some fluid from the bursa through a needle and/or inject corticosteroids into the bursa to calm the inflammation.
If bursitis is caused by infection, standard treatment includes draining the bursa (usually via needle aspiration) and administration of appropriate antibiotics.
Crystal-induced bursitis is treated similarly to crystal-induced arthritis, because the underlying pathology in both conditions is identical. For example, if uric acid crystals are found in bursal fluid, treatment for gout (a condition caused by uric acid crystals in the joints) would most likely alleviate the symptoms.
Chronic bursitis is usually addressed with anti-inflammatory medications, corticosteroid injections, physical therapy and range-of-motion exercises. Rest and splinting may be relatively contraindicated in such cases, as adjacent joints might already exhibit fibrosis and restricted range of motion.
When bursitis fails to respond to the usual modes of therapy, surgical excision of the bursal sac may be necessary to preserve function in adjacent structures.
Bursitis is a common cause of pain in and around joints. Its diagnosis and treatment are usually straightforward, and most patients recover and do well. Complicated or chronic cases can lead to disability, however, and surgical management or long-term physical and occupational therapy are occasionally indicated.
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