ICD-10-CM M71.16 other infective bursitis knee region
SNOMED CT terminology prepatellar bursitis
SNOMED CT terminology septic bursitis
Laboratory Tests
When infection is possible
Infection workup
Bursal fluid analysis if aspiration performed
Gram stain
Aerobic culture
Cell count with differential
Predominant neutrophils supporting infection
Crystal analysis
Monosodium urate crystals
Calcium pyrophosphate crystals
Blood tests for systemic illness
Complete blood count for leukocytosis
C reactive protein for inflammation trend
ESR for inflammation trend
Limited specificity
Blood cultures if febrile or toxic
When hemorrhage or procedure planned
Procedural context
Coagulation studies if anticoagulated and aspiration planned
Serum glucose if diabetic or systemic infection
PITFALLS
PITFALLS
Normal white blood cell count does not exclude septic bursitis
CRP and ESR support inflammation but do not localize source
Crystals can coexist with infection
Diagnostic Tests
Scoring Systems
Clinical decision structure
Septic bursitis probability framing
Fever or systemic symptoms
Overlying cellulitis
Skin break over bursa
Immunocompromised state
Failure of conservative therapy
Septic arthritis red flag framing
Severe pain with passive motion
Large intra-articular effusion
Inability to bear weight
Lower threshold for arthrocentesis
Radiographs
X-ray indications
Trauma mechanism
Patellar fracture concern
Persistent pain
Foreign body concern with puncture
Typical views
Knee 3-view series
MRI
MRI indications
Failure of conservative management with unclear diagnosis
Deep infection concern
Osteomyelitis concern
Abscess beyond superficial bursa
Internal derangement concern
Meniscal or ligament injury
CT
CT indications
Complex fracture concern when X-ray limited
Deep abscess mapping when MRI unavailable
Foreign body localization when radiolucent concern
Disposition
Discharge vs admission
Discharge criteria
Aseptic features
No fever
Minimal erythema
Preserved knee passive range of motion
Pain controlled with oral plan
Reliable follow-up
No rapidly progressive skin findings
Admission criteria
Systemic toxicity
Hemodynamic instability
Immunocompromised state with suspected infection
Failed oral antibiotics
Extensive cellulitis
Need for IV antibiotics
Concern for septic arthritis or osteomyelitis
Follow-up timing
Follow-up plan
Aseptic bursitis
Primary care or sports medicine in 1 to 2 weeks if persistent
Suspected or confirmed septic bursitis
Reassessment in 24 to 48 hours
Culture follow-up and antibiotic adjustment
Treatment
Immediate life-saving interventions
High-risk infection pathway
If septic shock concern, sepsis bundle per local protocol
If septic arthritis concern, immediate arthrocentesis pathway and orthopedic consultation
Immobilization and Splinting
Activity modification and support
Avoid kneeling and direct pressure
Protective knee padding
Compression wrap
Avoid excessive tightness
Short-term immobilizer only if severe pain
Encourage gentle range of motion when tolerated
Reduction
Not applicable pathway
No reduction indications for isolated prepatellar bursitis
Open fracture medications and timing
Not applicable pathway
Open fracture protocols not applicable unless concomitant injury
DVT prophylaxis when relevant
Not typically indicated
Routine pharmacologic prophylaxis not indicated for isolated bursitis
Consider if prolonged immobilization and high VTE risk by local protocol
Aseptic bursitis management
Conservative care
Rest and activity modification
Ice
10 to 20 minutes per session
Several sessions per day
Compression and elevation
NSAID options
Ibuprofen PO 400 mg to 600 mg every 6 hours as needed
Naproxen PO 250 mg to 500 mg every 12 hours as needed
Topical diclofenac per product labeling
Acetaminophen option
Acetaminophen PO 500 mg to 1000 mg every 6 hours as needed
Maximum daily dose per local protocol and liver risk
Aspiration considerations
Large tense bursa with functional limitation
Diagnostic uncertainty for infection or crystals
Hemorrhagic bursa suspicion
Post aspiration compression wrap
Reduced recurrence
Corticosteroid injection considerations
Persistent aseptic bursitis after conservative therapy
Avoid if any infection concern
Avoid repeated injections due to skin atrophy risk
Suspected or confirmed septic bursitis
Antibiotic strategy
Empiric coverage targets
Staphylococcus aureus
Streptococcus pyogenes
Oral regimen for mild illness and reliable follow-up
Cephalexin PO 500 mg every 6 hours
Typical duration 7 to 14 days
Dicloxacillin PO 500 mg every 6 hours
Typical duration 7 to 14 days
If MRSA risk or beta lactam allergy
Trimethoprim sulfamethoxazole DS PO 1 tablet every 12 hours
Combine with beta lactam if streptococcal coverage needed
Doxycycline PO 100 mg every 12 hours
Combine with beta lactam if streptococcal coverage needed
Clindamycin PO 300 mg to 450 mg every 6 to 8 hours
IV regimen for systemic illness or unreliable follow-up
Vancomycin IV per weight based dosing and renal function
Trough and AUC monitoring per local protocol
Alternative IV options per local antibiogram and allergy profile
Drainage strategy
Aspiration for culture and decompression when feasible
Recurrent fluid reaccumulation
Repeat aspiration
Failure of antibiotics or loculated infection
Surgical drainage consideration
Bursectomy consideration
Evidence and guideline notes
Evidence notes
Empiric antibiotics for septic superficial bursitis covering Staphylococcus aureus and Streptococcus pyogenes
ACEP Level B recommendation for short-acting opioids as an option for short-term relief of acute musculoskeletal pain when appropriate
ACEP policy statement supports NSAID and acetaminophen as initial options for acute pain management
Special Populations
Pregnancy
Pregnancy considerations
Infection thresholds
Lower threshold for systemic evaluation if febrile
Analgesia selection
Acetaminophen preferred
NSAID avoidance in later pregnancy per obstetric guidance
Antibiotic selection
Beta lactams generally compatible
Avoid doxycycline
Geriatric
Geriatric considerations
Higher risk of medication adverse effects
NSAID renal and gastrointestinal risks
Lower threshold for admission with infection signs
Cellulitis progression monitoring
Mobility support needs
Pediatrics
Pediatric considerations
Traumatic mechanism evaluation
Patellar fracture vigilance
Dosing weight based
NSAIDs and acetaminophen per kg dosing
Infection considerations
Lower threshold for evaluation if refusal to bear weight
Background
Epidemiology
Epidemiology
Common superficial bursitis location at knee from kneeling and direct trauma
Higher prevalence in occupations with frequent kneeling
Septic bursitis more common in superficial bursae than deep bursae
Pathophysiology
Pathophysiology
Prepatellar bursa between patella and overlying skin
Repetitive microtrauma
Synovial lining inflammation
Fluid accumulation
Direct blow
Hemorrhagic bursitis
Infection route
Direct inoculation from skin break
Contiguous spread from cellulitis
Therapeutic Considerations
Therapeutic considerations
Compression after aspiration reduces reaccumulation risk
Steroid injection increases risk if occult infection present
Antibiotics are required for septic bursitis
Surgical drainage reserved for refractory or complicated infection
Patient Discharge Instructions
Copy discharge instructions
Discharge packet
Diagnosis explanation
Inflamed fluid sac in front of kneecap
Activity
Avoid kneeling and direct pressure
Use knee pad if unavoidable
Ice
10 to 20 minutes at a time
Several times daily
Compression and elevation
Snug wrap during day
Elevate above heart when resting
Pain control
NSAID plan if safe
Acetaminophen plan if needed
Wound care
Keep any abrasion clean and covered
Return to ED now
Fever
Rapidly worsening redness or swelling
Increasing pain
New drainage or pus
Inability to bend or straighten knee due to pain
Feeling faint or very unwell
Follow-up
If on antibiotics, reassessment in 24 to 48 hours
If not improving in 1 to 2 weeks, primary care or sports medicine
References
Evidence-based sources
Key sources
AAFP review on common superficial bursitis including septic bursitis empiric coverage targets
NCBI Bookshelf overview on septic bursitis diagnosis and management
Cleveland Clinic patient overview for prepatellar bursitis treatment options including antibiotics for infection
Orthobullets summary for prepatellar bursitis clinical diagnosis and nonoperative management
ACEP clinical policy on opioids for acute pain including Level B recommendation context for acute musculoskeletal pain
ACEP policy statement on optimizing acute pain treatment including NSAID and acetaminophen considerations
ACR practice parameter noting ultrasound utility for evaluation of superficial bursae around the knee
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.