Pre-patellar bursitis
Exam Tips
- Key discriminator: pre-patellar bursitis gives a focal superficial swelling over the patella with relatively preserved knee joint range, whereas septic arthritis usually causes globally painful restricted movement.
- In any hot swollen prepatellar bursa, aspirate early (before antibiotics if possible) for Gram stain, culture, and crystals; gout and infection can coexist.
- A normal white cell count does not exclude septic bursitis; integrate CRP/ESR trends, clinical progression, and aspiration results.
- Ask targeted exposure history (kneeling occupation, minor skin trauma) and comorbidity history (diabetes, steroids, immunosuppression) to stratify septic risk.
- Visual recognition matters in OSCEs: look for a dome-shaped, fluctuant swelling directly over the kneecap with overlying erythema (compare with standard MSK knee surface anatomy figures).
Definition
Pre-patellar bursitis is inflammation of the superficial bursa between the skin and the anterior patella, producing a localized swelling over the kneecap. It may be non-septic (typically due to repetitive kneeling, trauma, crystal disease, or inflammatory disease) or septic (usually bacterial), and this distinction is central because septic cases can progress to deep infection and systemic illness.
Pathophysiology
Mechanical irritation or direct trauma causes microvascular injury in the pre-patellar bursa, with increased capillary permeability, synovial-like lining hyperplasia, collagen deposition, and fluid accumulation in the bursal sac. Recurrent friction (for example prolonged kneeling) drives chronic wall thickening and recurrent effusions. In septic bursitis, organisms are usually inoculated through minor skin breaks or local spread (most commonly Staphylococcus aureus, then streptococci), triggering neutrophil-rich purulent inflammation; haematogenous spread is less common because bursal tissue is relatively poorly vascularized. Crystal arthropathy (urate or CPPD) can also inflame the bursa and may coexist with infection, so crystal identification does not exclude sepsis.
Risk Factors
- Frequent kneeling occupations or hobbies (for example carpet laying, gardening, roofing, cleaning, mining)
- Acute direct knee trauma or repeated minor trauma
- Participation in sports with repeated knee impact/friction (for example wrestling, basketball)
- Gout or pseudogout
- Inflammatory rheumatic disease (for example rheumatoid arthritis, SLE, spondyloarthropathy, scleroderma)
- Immunocompromise (for example diabetes, systemic corticosteroid therapy, HIV, alcohol misuse)
- Recent bursal aspiration/injection or pre-existing bursal disease
- Bleeding tendency or anticoagulant therapy (risk of haemorrhagic bursal fluid)
Clinical Features
Symptoms
- Anterior knee swelling over the patella
- Localized pain or tenderness (may be mild/minimal in chronic non-septic cases)
- Redness and warmth over the kneecap
- Pain when kneeling and discomfort on extreme knee flexion
- Difficulty with walking or kneeling
- Fever or systemic upset suggests septic bursitis
Signs
- Focal, fluctuant, compressible swelling directly superficial to the patella
- Overlying erythema and local warmth (can occur in non-septic and septic disease)
- Point tenderness over bursa, often greater in septic cases
- Knee joint range usually largely preserved (helps distinguish from true intra-articular pathology)
- Cellulitis, abrasion, laceration, or puncture over bursa raises suspicion of infection
- Sepsis physiology in severe cases (tachycardia, hypotension, tachypnoea, pyrexia)
Investigations
Management
Lifestyle Modifications
- Relative rest, avoid kneeling and repetitive pressure, and use knee pads/activity modification
- Ice and elevation in early painful swelling
- Address occupational contributors and return-to-work plan to reduce recurrence
- Safety-net urgently for fever, spreading erythema, worsening pain, or systemic features
Pharmacological Treatment
Analgesia (non-septic or while awaiting results)
- Paracetamol 1 g orally every 4-6 hours when required (max 4 g/day)
- Ibuprofen 400 mg orally three times daily with/after food (use lowest effective dose, shortest duration)
Avoid/limit NSAIDs in CKD, peptic ulcer disease, heart failure, anticoagulation, or high GI/CV risk; consider gastroprotection where appropriate.
Oral antibiotics for suspected/confirmed septic pre-patellar bursitis (guided by local antimicrobial policy and cultures)
- Flucloxacillin 500 mg to 1 g orally four times daily
- If true penicillin allergy: Clarithromycin 500 mg orally twice daily
Typical course is 7-14 days depending on severity/response and microbiology. Aspirate before first antibiotic dose when feasible and safe. Escalate to IV therapy/admission if systemic toxicity, immunocompromise, rapidly progressive cellulitis, or failure of oral treatment.
Corticosteroid injection (selected non-septic refractory cases only)
- Hydrocortisone acetate intra-bursal injection (specialist practice, dose per local protocol)
Do NOT inject if septic bursitis is suspected or overlying skin infection is present. Risks include skin atrophy, depigmentation, tendon injury, bleeding, and iatrogenic infection/fistula.
Surgical / Interventional
- Needle aspiration for diagnostic confirmation and symptomatic decompression
- Repeat aspiration if re-accumulation in septic cases with close review
- Incision and drainage or bursectomy for persistent/recurrent septic bursitis or failure of conservative and antibiotic management
- Manage procedural risks: bleeding, secondary infection, poor wound healing, painful scar, reduced local sensation
Complications
- Bursal rupture
- Functional limitation with reduced work/sport participation
- Local cellulitis and soft tissue necrosis (especially septic disease)
- Septic arthritis from contiguous spread
- Sepsis
- Patellar osteomyelitis
- Procedure-related complications (bleeding, infection, patellar tendon injury, sinus/fistula, skin atrophy after steroid injection)
Prognosis
Most non-septic cases settle with conservative measures and do not require surgery. Septic pre-patellar bursitis usually resolves with prompt aspiration plus targeted antibiotics, but outcomes are worse and complications are more likely in people with diabetes, immunosuppression, or delayed treatment; recurrence risk falls with pressure avoidance and occupational modification.
Sources & References
✅NICE Guidelines(1)
- Pre-patellar bursitis[overview]