Bursitis

Basics

Bursae are synovial fluid-filled sacs:
- ∼150 are located between bones, ligaments, tendons, muscles, and skin
They provide lubrication to reduce friction during movement
Bursitis is inflammation of a bursa caused by trauma and overuse, infection, crystal deposition, or systemic disease
Chronic bursitis can lead to proliferative changes in the bursa
Commonly affected sites:
- Shoulder (subacromial)
- Elbow (olecranon): Usually secondary to trauma
- Hip (greater trochanter, ischial, iliopsoas): More common in elderly. Of note, trochanteric bursitis is less common than previously thought, more commonly pain is due to abductor tendinopathy
- Knee (prepatellar and pes anserine): Secondary to trauma or arthritis
- Foot (calcaneal): Almost always secondary to improperly fitting shoes/heels

Trauma (most common cause):
- Specific traumatic event or repetitive use of associated joints
- Adjacent tendon tear (e.g., acute shoulder cuff tear)
Infection: Secondary to direct penetration; may be obvious or microscopic:
- Higher risk with diabetes, chronic alcohol abuse, uremia, gout, immunosuppression
- 90% caused by Staphylococcus spp
Crystal deposition: Calcium phosphate, urate
Systemic disease: Rheumatoid arthritis, gout, ankylosing spondylitis, psoriatic arthritis, lupus, rheumatic fever

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