[3] Septic Arthritis

Question 1

What is septic arthritis?

Answer 1

Inflammation of a joint caused by bacterial infection

Question 2

What joints can be affected by septic arthritis?

Answer 2

Any joint can be affected, but it’s most common in the knees (>50% cases) and hips

Question 3

Why is septic arthritis a very important diagnosis?

Answer 3

Because it can destroy a joint in under 24 hours, and has a mortality rate of 11%

Question 4

What is the pathophysiology of septic arthritis?

Answer 4

Septic arthritis is commonly caused by bacteria reaching the synovial membrane of the joint, either by bloodstream transport from an infection elsewhere, direct penetration into the joint following arthrocentesis, arthroscopy, or trauma, or from a surrounding infection in the bone or tissue

Question 5

What are the risk factors for septic arthritis?

Answer 5

• Pre-existing joint disease, especially RA
• Diabetes mellitus
• Immunosuppression
• Chronic renal failure
• Recent joint surgery
• Prosthetic joint
• IV drug abuse
• Age >80 years

Question 6

What are the common causative organisms in septic arthritis?

Answer 6

• Staph. aureus
• Streptococci
• Neisseria gonococcus
• Gram -ve bacilli

Question 7

Describe the onset of symptoms in septic arthritis

Answer 7

The symptoms tend to develop quickly over a few hours or days

Question 8

What are the symptoms of septic arthrtis?

Answer 8

• Severe pain, swelling, redness, and heat in the affected joint
• Pyrexia and rigors
• Difficulty moving affected joint
• Prostration
• Vomiting
• Hypotension

Question 9

What investigations are done in septic arthritis?

Answer 9

• Urgent joint aspiration for synovial fluid microscopy and culture
• Plain radiographs (may be normal)
• CRP (may be normal)
• Blood cultures

Question 10

What are the differential diagnoses of septic arthritis?

Answer 10

• Gout
• RA
• Osteoarthritis
• Drug-induced arthritis
• Reactive arthritis
• Viral arthritis
• Infective endocarditis
• Lyme disease
• Vasculitis

Question 11

How is septic arthritis treated?

Answer 11

• Antibiotics
• Corticosteroids
• Joint drainage
• Splinting

Question 12

When should treatment with antibiotics be started in septic arthritis?

Answer 12

Empirical treatment should be started immediately, before the results of cultures are known

Question 13

What bacteria should the antibiotic used in the empirical treatment of septic arthritis cover?

Answer 13

At least S. Aureus and Streptococcus spp.

Question 14

Why should a microbiologist be consulted in the empirical treatment of septic arthritis?

Answer 14

To inform choice of therapy based on resistance patterns in local hospitals and the community

Question 15

How are antibiotics administered in septic arthritis?

Answer 15

They are initially given intravenously (usually for 2-3 weeks) before being switched to oral (often for a further 2-3 weeks)

Question 16

Is there any benefit in injecting antibiotics intra-articularly in septic arthritis?

Answer 16

No

Question 17

Why is there no benefit injecting antibiotics intra-articularly in septic arthritis?

Answer 17

• Antibiotics have good penetration across the synovial membrane
• Intra-articular injection has the potential for causing chemical synovitis

Question 18

What should be done if septic arthritis fails to respond to 5 days of treatment with appropriate antibiotic?

Answer 18

The therapeutic approach should be re-assessed, including re-examining the synovial fluid for crystals, and considering a synovial biopsy

Question 19

What is the role of corticosteroid treatment in septic arthritis?

Answer 19

Corticosteroids are known to have beneficial effects on the rate and extent of cartilage destruction in arthritis, which is important as chondral damage is one the major sequelae of septic arthritis

Question 20

When might joint drainage in septic arthritis be required?

Answer 20

If the infection does not respond to antibiotic treatment

Question 21

What may be required to drain joints that are difficult to access in septic arthrtiis?

Answer 21

Ultrasound-guided needle aspiration, or open arthrotomy

Question 22

In what position should the joint be splinted in septic arthritis?

Answer 22

In the position of functio n

Question 23

When should the splint be removed and the joint mobilised in septic arthritis?

Answer 23

Immediately after the infection is under control

Question 24

Why is immediate joint mobilisation important after septic arthritis?

Answer 24

It promotes the healing of articular cartilage, and prevents contractures