Bruised and Pus-Draining Knee: Causes, Immediate Care & When to Seek Help

A knee that is both bruised and draining pus indicates a likely infected wound or septic joint—this requires prompt medical evaluation. Do not delay.

Immediate First Aid

1. Clean gently: Wash with mild soap and water; pat dry.
2. Apply antibiotic ointment: Thin layer (bacitracin, polysporin) if not allergic.
3. Cover with sterile dressing: Non-stick pad + gauze + light wrap.
4. Elevate: Knee above heart level on pillows to reduce swelling.
5. Avoid weight-bearing: Use crutches/cane; do not kneel.
6. OTC pain relief: Ibuprofen (anti-inflammatory) or acetaminophen per label.

Red Flags Requiring Urgent Care

• Spreading redness, warmth, or red streaks (lymphangitis)
• Increasing swelling or pain despite elevation
• Fever ≥100.4°F (38°C) or chills
• Inability to bear any weight
• Visible joint deformity
• Pus increasing or foul-smelling
• Underlying conditions: diabetes, immunosuppression, prosthetic joint

Medical Evaluation Will Likely Include

• Wound culture to identify bacteria
• Blood work (CBC, CRP, ESR for infection markers)
• X-ray (rule out osteomyelitis, foreign body, fracture)
• Possible ultrasound or MRI if deep abscess suspected
• Joint aspiration if septic arthritis suspected

Potential Treatments

• Oral or IV antibiotics (targeted after culture)
• Incision and drainage of abscess
• Surgical washout if joint involved
• Wound care specialist referral for complex wounds

Do not attempt to drain pus yourself. Improper drainage can worsen infection. Seek care within 24 hours—or immediately if red flags present.