Septic Bursitis: Causes, Risk Factors, Symptoms, and Treatment

What Causes Septic Bursa?

Septic bursitis, also known as infectious bursitis, is primarily caused by a bacterial infection within a bursa, often resulting from bacteria entering the bursa through a break in the skin or, less commonly, via hematogenous spread.

Introduction to Bursae and Bursitis

To understand what causes septic bursitis, it's essential to first grasp the role of bursae in the body and the general concept of bursitis. Bursae are small, fluid-filled sacs located throughout the body, typically near joints, between bones, tendons, and muscles. Their primary function is to reduce friction and cushion pressure points between these moving parts, allowing for smooth, pain-free movement. Common locations include the shoulders, elbows, hips, and knees.

Bursitis is the inflammation of a bursa. This inflammation can arise from various factors, broadly categorized into two main types:

• Aseptic Bursitis (Non-infectious): This is the more common type, typically caused by repetitive stress, overuse, direct trauma, prolonged pressure, or underlying inflammatory conditions like rheumatoid arthritis or gout. The inflammation is mechanical or chemical, not due to an infection.
• Septic Bursitis (Infectious): This is a more serious condition where the bursa becomes infected by microorganisms, almost exclusively bacteria.

Understanding Septic Bursitis

Septic bursitis specifically refers to an infection of a bursa. Unlike aseptic bursitis, which often resolves with rest and anti-inflammatory measures, septic bursitis requires prompt medical intervention, primarily with antibiotics, to prevent severe complications. The presence of bacteria within the bursa's synovial fluid leads to a strong inflammatory response and the characteristic signs of infection.

The Primary Cause: Bacterial Invasion

The overwhelming majority of septic bursitis cases are caused by bacterial infection. The most common culprits include:

• Staphylococcus aureus (Staph): This bacterium is responsible for approximately 70-80% of all septic bursitis cases. Staph aureus is a common inhabitant of the skin and nasal passages, making it readily available to enter the body through breaks in the skin.
• Streptococcus species: These bacteria are also common skin flora and can cause septic bursitis, though less frequently than Staph aureus.
• Other Bacteria: Less commonly, other bacteria such as Gram-negative rods (e.g., Escherichia coli, Pseudomonas) may be involved, particularly in individuals who are immunocompromised, have specific medical conditions (like diabetes), or have been exposed in healthcare settings.

Once bacteria enter the bursa, they multiply within the synovial fluid, triggering an immune response that results in the inflammation, pain, and systemic symptoms associated with infection.

Common Entry Points for Bacteria

For bacteria to cause septic bursitis, they must gain entry into the bursa. The primary mechanisms include:

• Direct Skin Trauma: This is the most common route. Any break in the skin directly over or near a superficial bursa can allow bacteria to enter. This includes:
  • Cuts, scrapes, and abrasions: Even minor skin lesions.
  • Puncture wounds: From thorns, splinters, or needles.
  • Insect bites or stings: If the skin barrier is compromised.
  • Surgical incisions or injections: Though less common, contamination during medical procedures can introduce bacteria.
  • Skin conditions: Eczema, psoriasis, ulcers, or other dermatological issues that compromise skin integrity can provide an entry point.
• Hematogenous Spread (Bloodstream Infection): Less frequently, bacteria from a distant infection (e.g., a skin infection elsewhere on the body, a urinary tract infection, or even dental abscesses) can travel through the bloodstream and seed a bursa. This is more likely in individuals with compromised immune systems.

Risk Factors for Septic Bursitis

While direct bacterial entry is the cause, several factors can increase an individual's susceptibility to developing septic bursitis:

• Pre-existing Aseptic Bursitis: A bursa that is already inflamed from overuse or trauma may have compromised integrity, making it more vulnerable to bacterial invasion.
• Compromised Skin Integrity: Any condition that weakens the skin's protective barrier, such as chronic skin conditions (psoriasis, eczema), wounds, ulcers, or open sores near a bursa.
• Immunocompromised State: Individuals with weakened immune systems have a reduced ability to fight off infections. This includes those with:
  • Diabetes mellitus
  • HIV/AIDS
  • Chronic kidney disease
  • Alcoholism
  • Rheumatoid arthritis (especially if on immunosuppressants)
  • Corticosteroid use
  • Chemotherapy
• Occupational or Recreational Activities: Jobs or hobbies that involve repetitive pressure, friction, or trauma to superficial bursae can lead to aseptic bursitis, which then increases the risk of subsequent infection. Examples include:
  • Plumbers or roofers (kneeling, prepatellar bursa)
  • Gardeners (kneeling, prepatellar bursa)
  • Students or desk workers (leaning on elbows, olecranon bursa)
• Intravenous Drug Use: Increases the risk of bacteremia (bacteria in the bloodstream), which can lead to hematogenous spread to various body sites, including bursae.
• Previous Surgery: Especially near a bursa, if not properly healed or if there was a post-operative infection.

Common Locations for Septic Bursitis

Septic bursitis most commonly affects superficial bursae, as they are more exposed to external trauma and pressure. The most frequently involved sites include:

• Olecranon Bursa (Elbow): Located at the tip of the elbow. Often referred to as "student's elbow" or "baker's elbow."
• Prepatellar Bursa (Knee): Located over the kneecap. Commonly known as "housemaid's knee" or "carpenter's knee."
• Less commonly, other superficial bursae like the pes anserine bursa (inner knee) or greater trochanteric bursa (hip) can become infected. Deep bursae, such as the subacromial bursa in the shoulder, are less frequently affected by septic bursitis due to their protected location, but it can occur.

Recognizing the Signs and Symptoms

The signs and symptoms of septic bursitis often develop rapidly and are typically more severe than those of aseptic bursitis. They include:

• Localized Pain: Often intense and throbbing, worsening with movement or pressure.
• Significant Swelling: A noticeable enlargement of the affected bursa.
• Redness (Erythema): The skin over the bursa appears red and inflamed.
• Warmth: The affected area feels hot to the touch.
• Tenderness: Exquisite pain upon palpation.
• Fever and Chills: Systemic signs of infection, indicating the body's generalized response.
• Malaise: A general feeling of unwellness or fatigue.

Diagnosis and Treatment Overview

Diagnosis of septic bursitis typically involves a physical examination and aspiration of the bursal fluid. The fluid is then sent for laboratory analysis, including Gram stain, culture, and cell count, to identify the specific bacteria causing the infection and determine appropriate antibiotic treatment. Blood tests may also be performed to assess systemic inflammation.

Treatment for septic bursitis almost always involves antibiotics, often administered intravenously initially, followed by oral antibiotics. Drainage of the infected bursal fluid may also be necessary to relieve pressure and facilitate healing. In severe or chronic cases, surgical removal of the bursa (bursectomy) might be considered.

Prevention Strategies

Preventing septic bursitis primarily focuses on protecting the skin and managing risk factors:

• Protect Superficial Bursae: Use padding (e.g., knee pads, elbow pads) during activities that involve prolonged pressure or repetitive trauma to bursae.
• Proper Wound Care: Promptly and thoroughly clean and cover any cuts, scrapes, or open wounds, especially those located over or near bursae.
• Manage Underlying Conditions: Individuals with chronic diseases like diabetes should diligently manage their condition to minimize immune compromise.
• Maintain Good Hygiene: Regular hand washing and skin hygiene can reduce the presence of skin bacteria.
• Avoid Direct Trauma: Be mindful of activities that could cause direct injury to bursae.

When to Seek Medical Attention

Septic bursitis is a medical emergency that requires immediate attention. If you experience any of the following symptoms, especially if they develop rapidly or are accompanied by fever:

• Severe pain, swelling, redness, and warmth over a bursa.
• An open wound or skin infection near a joint.
• Systemic symptoms like fever, chills, or general malaise.

Prompt diagnosis and treatment are crucial to prevent the infection from spreading to surrounding tissues, joints (septic arthritis), or the bloodstream (sepsis), which can lead to severe and life-threatening complications.

Conclusion

Septic bursitis is a serious condition caused by bacterial infection of a bursa, most commonly Staphylococcus aureus, typically entering through a break in the skin. It is distinct from the more common aseptic bursitis and demands immediate medical diagnosis and treatment to prevent potentially severe complications. Understanding the causes and risk factors is key for both prevention and prompt recognition.