03 / Orthopedic Surgery · endoscopic
Arthroscopic washout of septic arthritis
Pus in a joint is an emergency for cartilage: the scope washes the knee with litres while the cultures are still growing.
Indication: Septic arthritis of the native knee, on aspiration findings and clinical picture; prosthetic joints follow different rules.
On the tray for this operation
Test yourself on the tray
Stage
1 / 4
Confirming and culturing
The joint is aspirated before antibiotics when possible: cell count, Gram stain, crystals, culture.
Watch for: Antibiotics before aspiration sterilising the culture
Why are we operating?
Washout of the septic knee removes the pus that is digesting cartilage: arthroscopic lavage clears the joint of bacteria, enzymes and debris while cultures direct the antibiotics that follow. The operation's urgency is the cartilage's: irreversible surface loss begins within days, which is why the septic joint is a same-day surgical diagnosis, not a rheumatology referral that matures.
Pulls toward surgery
Gives the team pause
Shared foundations
What the surgeon is thinking
Confirming and culturing
Why does the needle precede the antibiotics even in theatre?
The aspirate is the diagnosis and the treatment plan in one syringe: Gram stain, culture, crystals and cell count. Antibiotics given first can silence the culture, converting six weeks of targeted therapy into six weeks of educated guessing. Only genuine septic shock reverses the order, and then the notes say so.
Portals and inspection
What is the arthroscope actually assessing beyond pus?
The joint's stage: synovitis, fibrinous loculations, and the cartilage's condition grade the infection and calibrate prognosis. The tour is systematic, gutters, notch, both compartments, patellofemoral joint, because pus loculates exactly where a hurried scope does not look.
Lavage and debridement
How much washing is enough?
Litres, until the returning fluid runs clear and every recess has been rinsed: the mechanism is dilution and debridement of fibrin membranes, which shelter organisms from both immune cells and antibiotics. Volume and thoroughness, not any additive, do the work.
Drains, antibiotics, reassessment
What determines whether this washout was the last one?
The trajectory: pain, fever and inflammatory markers should fall convincingly within 48 to 72 hours. A knee that re-accumulates or a CRP that plateaus means a return to theatre, planned without embarrassment, repeat washouts are common and are management, not failure.
Decision points
Arthroscopic or open washout for this septic knee?
Arthroscopic
The knee's default: complete access, less morbidity, repeatable. The scope reaches recesses an arthrotomy bruises its way toward.
Open arthrotomy
For joints the scope serves poorly, late organised infections needing formal debridement, or where equipment and expertise dictate.
In the knee the arthroscope won this argument; in other joints (the hip especially) the answer differs by anatomy and age. The principle is constant: complete drainage and lavage of every recess, by whichever door achieves it.
Cultures return negative at 48 hours but the story and synovial count screamed sepsis.
Treat as culture-negative septic arthritis
Prior antibiotics, fastidious organisms and sampling error all silence cultures: the clinical syndrome, not the lab's silence, drives the course.
Stop antibiotics and reframe
Only when a true alternative (crystal disease with a convincing picture) is positively established, not merely available.
Culture-negative does not mean infection-negative: the decision to de-escalate is made on the whole picture with microbiology in the conversation. Meanwhile crystals found do not acquit, since gout and sepsis famously share joints.
Leaving the OR
The handoff
- Procedure
- Arthroscopic washout, right knee septic arthritis; 9 L lavage until clear
- Samples
- Aspirate pre-antibiotics: Gram-positive cocci; synovial biopsies and fluid to micro
- Antibiotics
- Empirical per protocol, to be tailored at culture
- Watch for
- 48-72h trajectory: effusion re-accumulating or CRP plateau earns a relook, not a shrug
A fictional educational patient, handed over the way real ones are.
The postoperative course
- POD 0-1Analgesia, elevation and early gentle motion: a septic joint stiffens by scarring, and movement within comfort protects the cartilage that survived.
- POD 2-3The verdict window: falling CRP and a settling knee say the washout won; anything else books the repeat.
- Week 1-6Antibiotics completed per microbiology, often intravenous then oral; physiotherapy rebuilds the quadriceps the effusion switched off.
- MonthsHonest follow-up of the joint's future: cartilage lost to the infection declares itself as early arthritis, and the delay-to-washout is usually the epitaph written in the surfaces.