Prepatellar bursitis is inflammation of the bursa anterior to the patella, most commonly caused by chronic microtrauma from repetitive kneeling ("housemaid's knee"). It has a minimum annual incidence of ~10/100,000, predominantly affecting males (80%) aged 40–60 years. Approximately two-thirds of cases are non-septic and one-third are septic. [1-2] The critical clinical task is distinguishing septic from non-septic bursitis, as this drives all management decisions.
1. History
- Mechanism: Repetitive kneeling (carpet layers, plumbers, roofers, gardeners, clergy), direct trauma/fall onto knee, or recent skin break/abrasion over the patella [1-2]
- Onset and timing: Insidious (chronic microtrauma) vs. acute (trauma, hemorrhagic, or septic)
- Pain characterization: Anterior knee pain worsened by kneeling or direct pressure; typically preserved range of motion unless severe swelling
- Progression: Gradual worsening suggests chronic bursitis; rapid onset with warmth/erythema raises concern for septic bursitis
- Associated symptoms: Fever, chills, malaise (septic); joint stiffness without true intra-articular involvement
- Important negatives: Absence of locking, catching, or giving way (which suggest intra-articular pathology); no pain with weight-bearing ambulation in isolated bursitis
2. Alarm Features
- Fever >37.8°C — strongly suggests septic bursitis [2]
- Rapidly progressive erythema, warmth, and tenderness with overlying skin breakdown or cellulitis [3]
- Prebursal skin temperature difference >2.2°C compared to contralateral side [2]
- Purulent drainage from the bursa or overlying wound
- Systemic toxicity (tachycardia, hypotension, rigors) — consider bacteremia or necrotizing soft tissue infection
- Immunocompromised state (diabetes, HIV, chronic steroid use) — lower threshold for aspiration and admission [3]
- Failure to improve after 48–72 hours of appropriate antibiotics
3. Medications
- NSAIDs (ibuprofen 400–600 mg TID or naproxen 500 mg BID): First-line for non-septic bursitis [1][4]
- Antibiotics for septic bursitis: Must cover Staphylococcus aureus (responsible for ~73–80% of cases) [3][5]
- Oral: Cephalexin 500 mg QID or dicloxacillin 500 mg QID; consider TMP-SMX or doxycycline if MRSA risk
- IV (if acutely ill): Vancomycin or nafcillin depending on local resistance patterns
- Duration: Minimum 14 days recommended; treatment <14 days associated with higher failure rates [3]
- Corticosteroid injection: May be considered for confirmed non-septic bursitis with high occupational/athletic demands, but high-quality evidence of benefit is lacking. Contraindicated if infection is suspected — risk of worsening septic bursitis [1-2]
- Avoid: Aspiration of chronic microtraumatic (non-septic) bursitis due to risk of iatrogenic infection [1]
4. Diet
- No specific dietary triggers for most cases
- If gout is the underlying cause, standard gout dietary counseling applies (limit purine-rich foods, alcohol, fructose-sweetened beverages)
- Adequate hydration and nutrition support wound healing in septic cases
5. Review of Systems
- Constitutional: Fever, chills, night sweats, weight loss (septic, inflammatory, or neoplastic causes)
- Musculoskeletal: Other joint swelling or pain (polyarticular gout, rheumatoid arthritis), history of gout flares
- Skin: Recent abrasions, lacerations, insect bites, or cellulitis over the knee
- Rheumatologic: Morning stiffness, symmetric joint involvement, rash (psoriasis, rheumatoid nodules)
- Infectious: Recent illness, immunosuppression, IV drug use
6. Collateral History and Family History
- Occupational history is critical — kneeling occupations are the most common cause [1-2]
- Recreational activities: Wrestling, volleyball, gardening
- Family history of gout, rheumatoid arthritis, or other crystal arthropathies
- Social context: Alcohol use (gout risk), immunosuppression, diabetes
7. Risk Factors
- Occupational kneeling: Carpet layers, plumbers, roofers, mechanics, clergy [1-2]
- Direct trauma to the anterior knee
- Skin disruption overlying the bursa (abrasions, lacerations, insect bites) — major risk for septic bursitis
- Male sex (80% of cases) [2]
- Age 40–60 years [2]
- Immunosuppression: Diabetes, chronic corticosteroid use, HIV, alcoholism [3]
- Underlying inflammatory conditions: Gout, rheumatoid arthritis [1]
- Prior bursitis episodes — recurrence is common
8. Differential Diagnosis
- Septic arthritis of the knee — the most dangerous mimic; distinguished by painful, limited range of motion in all planes and intra-articular effusion (not anterior bursal swelling). Bursitis preserves passive ROM [4][6]
- Cellulitis/abscess — overlapping erythema and warmth; ultrasound helps differentiate from bursitis [1]
- Gout/pseudogout — crystal-induced bursitis; aspirate with crystal analysis is diagnostic [1]
- Patellar fracture — post-traumatic; point tenderness over patella, inability to extend knee
- Infrapatellar bursitis — swelling is inferior to the patella rather than directly anterior
- Meniscal pathology or ligamentous injury — mechanical symptoms (locking, catching), joint line tenderness
- Morel-Lavallée lesion — post-traumatic closed degloving injury; MRI distinguishes
- Rheumatoid nodule or soft tissue tumor — firm, non-fluctuant mass; imaging and biopsy if atypical
9. Past Medical History
- Prior episodes of bursitis (recurrence risk)
- History of gout or pseudogout
- Rheumatoid arthritis or other inflammatory arthropathy
- Diabetes mellitus or immunosuppressive conditions
- Prior knee surgery or prosthetic hardware
- Anticoagulant use (hemorrhagic bursitis risk)
- History of MRSA infection or colonization
10. Physical Exam
- Inspection: Focal, well-circumscribed swelling anterior to the patella (not within the joint); erythema and warmth suggest septic or inflammatory etiology
- Palpation: Fluctuant, tender bursal swelling; assess for crepitus, overlying skin breaks, or draining sinuses
- Range of motion: Typically preserved passive and active ROM — this is a key distinguishing feature from septic arthritis. Flexion may be limited by tension from the distended bursa [4][6]
- Temperature: Compare skin temperature to contralateral knee; difference >2.2°C suggests infection [2]
- Vital signs: Fever >37.8°C raises concern for septic bursitis [2]
- Regional exam: Popliteal fossa (Baker's cyst), inguinal lymphadenopathy, assess for tracking cellulitis
- Joint exam: Ensure no intra-articular effusion (ballottement, patellar tap) — if present, consider septic arthritis
11. Lab Studies
- Non-septic bursitis: Labs generally not needed for straightforward cases
- If septic bursitis suspected:
- Bursal fluid aspiration — the key diagnostic test: [1-2][5]
- Cell count: WBC >3,000 cells/μL with >50% PMNs suggests infection
- Gram stain and culture (Staph aureus in ~73–80% of cases)
- Crystal analysis (rule out gout/pseudogout)
- Glucose: Fluid-to-serum glucose ratio <50% suggests infection
- Blood tests: CBC with differential, CRP, ESR (elevated but non-specific) [1]
- Blood cultures: If febrile or systemically ill
- Monitoring: Repeat aspiration may be needed in 24–48 hours if septic bursitis is being managed conservatively to assess response
12. Imaging
- First-line: Plain radiographs of the knee — rule out fracture, foreign body, or underlying bony pathology; usually normal in bursitis
- Ultrasound: Excellent for confirming bursal fluid collection, distinguishing bursitis from cellulitis, and guiding aspiration [1][5]
- MRI: Rarely needed acutely; useful for distinguishing infectious from non-infectious causes, evaluating for osteomyelitis, or assessing atypical presentations [1]
- CT: Generally not indicated unless concern for bony involvement
- When imaging is unnecessary: Clinically obvious non-septic bursitis with classic history and exam
13. Special Tests
- Bursal aspiration: Both diagnostic and therapeutic; use sterile technique to minimize iatrogenic infection risk [1-2]
- Point-of-care ultrasound (POCUS): Confirm fluid collection, guide aspiration, differentiate from cellulitis or abscess
- Crystal analysis under polarized light microscopy: Negatively birefringent (gout) vs. positively birefringent (pseudogout)
- No validated scoring system exists specifically for prepatellar bursitis, but clinical criteria (fever, skin lesion, bursal WBC >3,000, positive Gram stain) guide the septic vs. non-septic distinction [2]
14. ECG
- Not routinely indicated
- Consider if the patient is septic or hemodynamically unstable (tachycardia, hypotension) as part of a sepsis workup
15. Assessment
Severity stratification
- Mild/Non-septic: Focal swelling, no systemic signs, preserved ROM → conservative management
- Moderate/Septic (non-toxic): Warmth, erythema, mild fever, no systemic toxicity → aspiration + outpatient oral antibiotics with close follow-up [1][3]
- Severe/Septic (toxic): High fever, extensive cellulitis, systemic illness, immunocompromised → admission for IV antibiotics [1][3]
Approximately one-third of inflammatory bursitis cases are septic. [2][7] Staphylococci account for ~73% and streptococci for ~19% of culture-positive cases. [3] The overall failure rate with appropriate treatment is low (~5.9%). [3]
16. Treatment Plan
Non-septic bursitis
- PRICE protocol: Protection, Rest, Ice, Compression (elastic wrap), Elevation [2][8]
- NSAIDs: Ibuprofen 400–600 mg TID or naproxen 500 mg BID for 7–14 days
- Activity modification: Avoid kneeling; use knee pads when kneeling is unavoidable [1]
- Aspiration: For large, tense effusions causing significant discomfort; avoid routine aspiration of chronic microtraumatic bursitis (iatrogenic infection risk) [1]
- Corticosteroid injection: Consider for refractory non-septic cases with high functional demands (e.g., methylprednisolone 40 mg or triamcinolone 40 mg intrabursal); evidence of benefit is limited [1][4]
Septic bursitis
- Aspiration: Diagnostic and therapeutic; may need serial aspirations every 24–48 hours [2]
- Antibiotics: Anti-staphylococcal coverage for minimum 14 days [3]
- Non-toxic: Oral cephalexin 500 mg QID or dicloxacillin 500 mg QID; add MRSA coverage (TMP-SMX DS BID or doxycycline 100 mg BID) if risk factors present
- Toxic/febrile/extensive cellulitis: IV vancomycin (if MRSA concern) or IV nafcillin/oxacillin [1][3]
- Surgery: Reserved for refractory cases not responding to antibiotics ± serial aspiration, or recurrent septic bursitis. Endoscopic bursectomy is non-inferior to open bursectomy with shorter hospital stays and fewer wound complications [9-10]
17. Disposition
- Discharge: Non-septic bursitis; septic bursitis in non-toxic, immunocompetent patients who can tolerate oral antibiotics and have reliable follow-up [1]
- Observation/Admission: Septic bursitis with fever, extensive cellulitis, systemic toxicity, immunocompromised status, failed outpatient therapy, or inability to tolerate oral medications [1][3]
- Surgical consultation: Refractory septic bursitis not responding to 48–72 hours of antibiotics and serial aspiration; recurrent bursitis; concern for necrotizing infection [9-10]
- Rheumatology consultation: Suspected crystal arthropathy or underlying inflammatory condition
18. Follow Up / Return Precautions
- Follow-up timing: Septic bursitis managed as outpatient should be reassessed in 24–48 hours for clinical response and possible repeat aspiration. Non-septic bursitis: follow-up in 1–2 weeks [2]
- Return precautions — instruct patients to return immediately for:
- Worsening redness, swelling, or pain
- New or worsening fever/chills
- Red streaking from the knee
- Inability to bear weight or new joint stiffness
- Patient counseling:
- Use knee pads for occupational or recreational kneeling to prevent recurrence [1]
- Complete the full antibiotic course if prescribed
- Avoid kneeling until fully resolved
- Expected recovery: Non-septic bursitis typically resolves in 2–4 weeks with conservative measures. Septic bursitis resolves in the majority of cases with appropriate antibiotics (failure rate ~5.9%), though treatment duration <14 days is associated with higher recurrence [3]
References
1. Common Superficial Bursitis. — Khodaee M. American Family Physician. 2017.
2. Prepatellar and Olecranon Bursitis: Literature Review and Development of a Treatment Algorithm. — Baumbach SF, Lobo CM, Badyine I, Mutschler W, Kanz KG. Archives of Orthopaedic and Trauma Surgery. 2014.
3. Clinical Characteristics and Management of Olecranon and Prepatellar Septic Bursitis in a Multicentre Study. — Charret L, Bart G, Hoppe E, et al. The Journal of Antimicrobial Chemotherapy. 2021.
4. Four Common Types of Bursitis: Diagnosis and Management. — Aaron DL, Patel A, Kayiaros S, Calfee R. The Journal of the American Academy of Orthopaedic Surgeons. 2011.
5. Management of Septic Bursitis. — Lormeau C, Cormier G, Sigaux J, Arvieux C, Semerano L. Joint Bone Spine. 2019.
6. Septic Bursitis in the Prepatellar and Olecranon Bursae: An Analysis of 25 Cases. — Ho G, Tice AD, Kaplan SR. Annals of Internal Medicine. 1978.
7. 2023 French Recommendations for Diagnosing and Managing Prepatellar and Olecranon Septic Bursitis. — Darrieutort-Laffite C, Coiffier G, Aïm F, et al. Joint Bone Spine. 2024.
8. Lower Extremity Bursitis. — Butcher JD, Salzman KL, Lillegard WA. American Family Physician. 1996.
9. Management of Septic and Aseptic Prepatellar Bursitis: A Systematic Review. — Brown OS, Smith TO, Parsons T, Benjamin M, Hing CB. Archives of Orthopaedic and Trauma Surgery. 2022.
10. Surgical Outcomes in Endoscopic Versus Open Bursectomy of the Septic Prepatellar or Olecranon Bursa. — Meade TC, Briones MS, Fosnaugh AW, Daily JM. Orthopedics. 2019.