Reactive Arthritis vs. Bursitis: Understanding Differences, Causes, and Treatments

What is the difference between reactive arthritis and bursitis?

Reactive arthritis is a systemic autoimmune condition triggered by an infection elsewhere in the body, causing widespread joint inflammation and often affecting other systems, whereas bursitis is a localized inflammation of a bursa, typically caused by overuse, trauma, or infection directly at the site.

Understanding Reactive Arthritis

Reactive arthritis, formerly known as Reiter's syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body, most commonly the gastrointestinal or genitourinary tracts. It is considered an autoimmune condition because the body's immune system, attempting to fight off the initial infection, mistakenly attacks its own healthy tissues, primarily the joints.

• Definition: A sterile inflammatory arthritis that arises days to weeks after an extra-articular infection, characterized by inflammation of joints, tendons, and sometimes other organs.
• Causes and Triggers: The primary triggers are bacterial infections.
  • Gastrointestinal infections: Often caused by Salmonella, Shigella, Yersinia, or Campylobacter.
  • Genitourinary infections: Most commonly caused by Chlamydia trachomatis.
  • Genetic Predisposition: Individuals carrying the HLA-B27 gene are significantly more susceptible to developing reactive arthritis after exposure to these infections.
• Common Symptoms: Symptoms typically appear 1-4 weeks after the initial infection.
  • Asymmetrical Arthritis: Affects a few joints, often large joints of the lower limbs (knees, ankles, feet) in an asymmetrical pattern. Inflammation can be severe, leading to pain, swelling, warmth, and redness.
  • Enthesitis: Inflammation where tendons or ligaments attach to bone, commonly seen in the Achilles tendon (causing heel pain) or plantar fascia (plantar fasciitis).
  • Dactylitis ("Sausage Digit"): Swelling of an entire finger or toe.
  • Extra-articular Manifestations:
    • Ocular: Conjunctivitis (red eyes), uveitis (eye pain, blurred vision).
    • Genitourinary: Urethritis (painful urination), cervicitis.
    • Dermatological: Keratoderma blennorrhagicum (skin lesions resembling psoriasis, especially on palms and soles), circinate balanitis (penile lesions).
    • Systemic: Fatigue, fever, weight loss.
• Affected Joints: Primarily affects the large joints of the lower extremities (knees, ankles, feet), but can also involve the spine (sacroiliitis) and upper limbs.

Understanding Bursitis

Bursitis is a common musculoskeletal condition characterized by the inflammation of a bursa. Bursae (plural of bursa) are small, fluid-filled sacs located throughout the body, acting as cushions between bones, tendons, muscles, and skin. Their primary function is to reduce friction and allow smooth movement of these structures over one another.

• Definition: Inflammation of a bursa, leading to pain, swelling, and tenderness in the affected area.
• Causes and Triggers:
  • Repetitive Motion or Overuse: The most common cause, due to repeated friction or pressure on a bursa (e.g., kneeling for long periods, repetitive throwing motions).
  • Trauma: A direct blow or injury to a bursa.
  • Prolonged Pressure: Leaning on elbows, prolonged sitting.
  • Infection (Septic Bursitis): Bacteria can enter the bursa through a cut or puncture wound, leading to a more severe, often red and hot, inflammation.
  • Underlying Medical Conditions: Gout, rheumatoid arthritis, diabetes can predispose individuals to bursitis.
• Common Symptoms:
  • Localized Pain: Often sharp initially, progressing to a dull ache, worsened by movement or pressure.
  • Swelling: Noticeable lump or puffiness over the affected bursa.
  • Tenderness: Pain upon touching the inflamed bursa.
  • Redness and Warmth: Especially prominent in septic bursitis, indicating infection.
  • Limited Range of Motion: Pain may restrict movement of the adjacent joint.
• Affected Bursae: Common sites include:
  • Shoulder: Subacromial bursa (deltoid bursitis).
  • Elbow: Olecranon bursa ("student's elbow").
  • Hip: Trochanteric bursa ("trochanteric bursitis").
  • Knee: Prepatellar bursa ("housemaid's knee"), infrapatellar bursa ("clergyman's knee"), pes anserine bursa.
  • Heel: Retrocalcaneal bursa.

Key Distinctions: Reactive Arthritis vs. Bursitis

The fundamental difference lies in their nature: reactive arthritis is a systemic, immune-mediated disease, while bursitis is a localized inflammatory condition.

• Underlying Cause:
  • Reactive Arthritis: Triggered by an infection elsewhere in the body, leading to a systemic immune response.
  • Bursitis: Primarily caused by local mechanical stress (overuse, trauma) or localized infection of the bursa itself.
• Nature of Inflammation:
  • Reactive Arthritis: A sterile inflammation of the synovial lining of joints (synovitis), entheses, and other tissues, part of a broader autoimmune reaction.
  • Bursitis: Direct inflammation of the bursa sac, which can be sterile or septic.
• Pattern of Joint Involvement:
  • Reactive Arthritis: Typically affects multiple joints (oligoarthritis), often asymmetrical, migratory (pain shifting from one joint to another), and primarily in the lower limbs. It can also involve the spine.
  • Bursitis: Almost always localized to a single bursa, though multiple bursae can be affected if there are multiple sites of overuse or injury.
• Associated Symptoms:
  • Reactive Arthritis: Frequently presents with extra-articular symptoms affecting the eyes, skin, genitourinary tract, and systemic symptoms like fever and fatigue.
  • Bursitis: Symptoms are generally confined to the immediate area around the inflamed bursa, though severe pain might limit adjacent joint movement. Systemic symptoms are rare unless the bursitis is septic and the infection has spread.
• Diagnostic Approach:
  • Reactive Arthritis: Requires a thorough history of recent infections, specific blood tests (e.g., ESR, CRP, HLA-B27, tests for causative organisms), and imaging (X-rays, MRI) to assess joint and enthesial inflammation.
  • Bursitis: Primarily diagnosed based on physical examination and localized symptoms. Imaging (ultrasound, MRI) can confirm bursa inflammation. Aspiration of bursa fluid may be performed to rule out infection (septic bursitis) or crystal deposition (gout).

Diagnostic Approaches

Accurate diagnosis is crucial for appropriate management.

• Reactive Arthritis:
  • Clinical History: Detailed inquiry about recent gastrointestinal or genitourinary infections, and the onset and pattern of joint pain.
  • Physical Examination: Assessment of joint swelling, tenderness, range of motion, and examination for extra-articular manifestations (eyes, skin).
  • Laboratory Tests:
    • Inflammatory Markers: Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
    • Infection Screening: Stool cultures, urine tests, or urethral/cervical swabs to identify a causative bacterial infection.
    • Genetic Marker: HLA-B27 testing (positive in 30-50% of cases).
    • Synovial Fluid Analysis: May show inflammatory fluid but no bacteria (sterile inflammation).
  • Imaging: X-rays, ultrasound, or MRI can show joint effusions, enthesitis, or sacroiliitis.
• Bursitis:
  • Clinical History and Physical Examination: Key for diagnosis, identifying localized pain, swelling, tenderness, and any activities that exacerbate symptoms.
  • Imaging:
    • Ultrasound: Excellent for visualizing fluid in the bursa, thickness of the bursa walls, and guiding aspiration.
    • MRI: Provides detailed views of soft tissues, helpful in differentiating bursitis from other conditions.
  • Bursa Fluid Aspiration: If infection (septic bursitis) or gout is suspected, fluid can be aspirated and sent for:
    • Cell Count and Differential: To assess inflammation.
    • Gram Stain and Culture: To identify bacterial infection.
    • Crystal Analysis: To check for urate or calcium pyrophosphate crystals.

Treatment Strategies

Treatment differs significantly due to the differing etiologies.

• Reactive Arthritis: Aims to manage symptoms, treat the underlying infection (if ongoing), and prevent chronic complications.
  • Antibiotics: To treat the initial bacterial infection, if still present. However, antibiotics do not typically resolve the joint symptoms once reactive arthritis has developed.
  • Nonsteroidal Anti-inflammatory Drugs (NSAIDs): First-line for pain and inflammation.
  • Corticosteroids: Oral or injected corticosteroids may be used for severe inflammation.
  • Disease-Modifying Antirheumatic Drugs (DMARDs): Such as sulfasalazine or methotrexate, may be used for persistent or severe arthritis.
  • Biologic Agents: In severe, refractory cases, TNF-alpha inhibitors may be considered.
  • Physical Therapy: Crucial for maintaining joint mobility, strength, and function, and for managing enthesitis.
• Bursitis: Focuses on reducing inflammation and pain, and addressing the cause.
  • Rest and Activity Modification: Avoiding activities that aggravate the bursa.
  • Ice: Application to reduce swelling and pain.
  • NSAIDs: Oral anti-inflammatory medications.
  • Corticosteroid Injections: Direct injection into the bursa can rapidly reduce inflammation and pain.
  • Physical Therapy: To improve flexibility, strengthen surrounding muscles, and correct biomechanical imbalances that contribute to bursitis.
  • Antibiotics: For septic bursitis, a course of antibiotics is essential.
  • Aspiration: Draining fluid from the bursa can relieve pressure and pain, especially in septic bursitis.
  • Surgery: Rarely needed, but bursectomy (surgical removal of the bursa) may be considered for chronic, recurrent, or infected bursitis that doesn't respond to other treatments.

When to Seek Professional Medical Advice

Consult a healthcare professional if you experience:

• Persistent joint pain, swelling, or stiffness that doesn't improve with rest.
• Redness, warmth, or significant tenderness around a joint or bursa.
• Fever, chills, or general malaise accompanying joint symptoms.
• Symptoms that appear after a recent infection or injury.
• Inability to move a joint or bear weight.

Early and accurate diagnosis is critical for both conditions to ensure appropriate management and prevent potential long-term complications.