What are the key findings and treatment options for an adult patient with a history of trauma or repetitive knee strain presenting with infrapatellar knee bursitis?

Infrapatellar Knee Bursitis Physical Exam Documentation

For infrapatellar bursitis, document localized swelling and tenderness either anterior to the patellar tendon (superficial) or posterior to the distal patellar tendon at the tibial tuberosity (deep), with pain on resisted knee extension and kneeling. 1, 2

Key Physical Exam Findings to Document

Inspection

• Visible swelling anterior to the patellar tendon (superficial infrapatellar bursa) or less visible if deep infrapatellar bursa is involved 1, 2
• Erythema or warmth if inflammatory or septic bursitis is present 1
• Skin changes from chronic kneeling or trauma 1, 3

Palpation

• Point tenderness directly over the tibial tuberosity and distal patellar tendon for deep infrapatellar bursitis 2, 3
• Fluctuant mass anterior to the patellar tendon for superficial infrapatellar bursitis 1, 4
• Absence of joint line tenderness to distinguish from intra-articular pathology 5

Range of Motion

• Pain with passive knee flexion beyond 90 degrees, which compresses the bursa 2, 3
• Pain with resisted knee extension due to patellar tendon tension over the inflamed bursa 2
• Full range of motion preserved (unlike arthritis or meniscal pathology) 5

Special Tests

• Kneeling test: Reproduce pain by having patient kneel directly on the affected knee 1, 3
• Patellar tendon palpation: Assess for concurrent patellar tendinopathy, which commonly coexists with deep infrapatellar bursitis 2

Critical Distinctions to Document

Rule Out Septic Bursitis

• Fever, systemic symptoms, or acute illness warrant immediate aspiration 1
• Severe erythema extending beyond bursa margins suggests infection 1
• Recent penetrating trauma or immunocompromise increases septic risk 1

Differentiate from Other Pathology

• Joint effusion would suggest intra-articular pathology rather than isolated bursitis 6
• Inability to bear weight or flex to 90 degrees requires radiographs per Ottawa criteria to exclude fracture 7, 8
• Bony tenderness at tibial tuberosity in adolescents suggests Osgood-Schlatter disease rather than simple bursitis 7

Treatment Algorithm Based on Exam Findings

Non-Septic, Traumatic/Hemorrhagic Bursitis

• Conservative management: Ice, elevation, rest, and NSAIDs 1, 5
• Aspiration may shorten symptom duration but is not mandatory 1
• Avoid corticosteroid injection in acute traumatic cases 1

Chronic Microtraumatic Bursitis

• Activity modification to eliminate repetitive kneeling 1, 2
• Eccentric exercises for rehabilitation, especially if patellar tendinopathy coexists 2
• Avoid routine aspiration due to iatrogenic infection risk 1
• Consider corticosteroid injection only for refractory cases, though high-quality evidence is lacking 1, 3

Inflammatory Bursitis (Gout, Rheumatoid Arthritis)

• Treat underlying condition as primary intervention 1
• Intrabursal corticosteroid injections are commonly used 1
• Consider PRP or PRP+HA for refractory cases, with emerging evidence showing reduced recurrence compared to corticosteroids alone 3

Septic Bursitis

• Mandatory aspiration with Gram stain, culture, cell count, glucose, and crystal analysis 1
• Outpatient oral antibiotics covering Staphylococcus aureus if patient is not acutely ill 1
• Hospital admission with IV antibiotics if systemically ill 1
• Surgical excision reserved for antibiotic-refractory or recurrent cases 1, 5

Imaging Considerations

Ultrasound is the preferred initial imaging modality to confirm bursitis, distinguish from cellulitis, and guide aspiration if needed 7, 6, 2. On ultrasound, deep infrapatellar bursitis appears as an anechoic fluid-filled structure immediately posterior to the distal patellar tendon and anterior to the tibial tuberosity 2. MRI with contrast can detect associated patellar tendinopathy, Hoffa's disease, and synovitis thicker than 2mm, but is not routinely indicated unless diagnosis is uncertain or multiple pathologies are suspected 7.

Common Pitfalls

• Do not aspirate chronic microtraumatic bursitis routinely, as this increases infection risk without clear benefit 1
• Do not inject corticosteroids into retrocalcaneal bursa (different location), as this may damage the Achilles tendon, but this concern does not apply to infrapatellar bursae 5
• Do not assume functional diagnosis without excluding septic bursitis if any signs of infection are present 1
• Document whether superficial or deep infrapatellar bursa is involved, as treatment approaches and prognosis may differ 1, 2, 3