Septic Arthritis

Question 1

… arthritis is an infection of one or more joints.

Answer 1

Septic arthritis is an infection of one or more joints.

Question 2

Bacterial infection is by far the most common cause of septic arthritis with… most frequently isolated. It normally presents with pain and swelling of the affected joint with signs of systemic infection.

Answer 2

Bacterial infection is by far the most common cause of septic arthritis with staphylococcus aureus most frequently isolated. It normally presents with pain and swelling of the affected joint with signs of systemic infection.

Question 3

Is septic arthritis common?

Answer 3

Septic arthritis is rare, it has an estimated incidence of 4-10 per 100,000 patient-years in Western Europe.
It most commonly affects the extremes of age (children and the elderly). It is also more common in those with immunodeficiency or IV drug use.

Question 4

Staphylococcus aureus is a gram-positive cocci and the most common cause of septic … in adults (accounting for 35-56% of cases) and children above the age of 2.

Answer 4

Staphylococcus aureus is a gram-positive cocci and the most common cause of septic arthritis in adults (accounting for 35-56% of cases) and children above the age of 2.

Question 5

There is increasing incidence of methicillin-resistant staphylococcus aureus (MRSA), particularly in what two populations?

Answer 5

. There is increasing incidence of methicillin-resistant staphylococcus aureus (MRSA), particularly in the intravenous drug user (IVDU) and elderly populations.

Question 6

Septic arthritis arises when bacteria (or other pathogens) enter the ….

Answer 6

Septic arthritis arises when bacteria (or other pathogens) enter the synovium.

Question 7

… spread is the most common mechanism by which bacteria infect the joint. Bacteria in the bloodstream seed into a joint and infection results.

Answer 7

Haematogenous spread is the most common mechanism by which bacteria infect the joint. Bacteria in the bloodstream seed into a joint and infection results.

Question 8

Direct … can occur during surgery, secondary to animal bites, wounds or rarely joint injection. Spread can also occur due to the spread from neighbouring infective foci.

Answer 8

Direct inoculation can occur during surgery, secondary to animal bites, wounds or rarely joint injection. Spread can also occur due to the spread from neighbouring infective foci.

Question 9

The synovium is a specialised membrane that is well vascularised and lacks a basement membrane. The lack of a limiting … membrane makes it susceptible to infection.

Answer 9

The synovium is a specialised membrane that is well vascularised and lacks a basement membrane. The lack of a limiting basement membrane makes it susceptible to infection.

Question 10

… … infection (PJI) represents an uncommon but serious complication of surgery.

Answer 10

Prosthetic joint infection (PJI) represents an uncommon but serious complication of surgery.

Question 11

… occurs in around 0.5-1% of hip replacements and 0.5-2% of knee replacements. If it occurs it commits the patient to long courses of antibiotics, further surgical intervention and often lengthy hospital stays.

Answer 11

PJI occurs in around 0.5-1% of hip replacements and 0.5-2% of knee replacements. If it occurs it commits the patient to long courses of antibiotics, further surgical intervention and often lengthy hospital stays.

Question 12

Septic arthritis is more frequently seen in what type of patients?

Answer 12

Septic arthritis is more frequently seen in elderly diabetic patients.

Question 13

What are 5 risk factors for developing septic arthritis?

Answer 13

Diabetes
Advancing age
Prosthesis
Immunodeficiency / immunosuppression
IV drug abuse (consider resistant organisms and pseudomonas)

Question 14

A high index of suspicion should be had for … … in any patient presenting with acute atraumatic joint pain.

Answer 14

A high index of suspicion should be had for septic arthritis in any patient presenting with acute atraumatic joint pain.

Question 15

Symptoms of septic arthritis (4)

Answer 15

Pain
Swelling
Fevers
Inability to weight bear

Question 16

Signs of septic arthritis (5)

Answer 16

Pain on active and passive movement
Reduced ROM (range of motion)
Erythema
Warmth
Joint effusion

Question 17

Differential diagnosis - septic arthritis

Answer 17

A number of conditions may present with a similar clinical picture. Excluding septic arthritis is essential.

Rheumatoid arthritis
Osteoarthritis
Crystal arthropathies (gout, pseudogout)
Drug-induced arthritis
Haemarthrosis
Reactive arthritis
Lyme disease

Question 18

Investigations in septic arthritis: what is key?

Answer 18

Joint aspiration is key and should be obtained prior to antibiotics (whenever possible).

Question 19

What will blood tests show in septic arthritis?

Answer 19

Blood tests will normally show an elevated CRP and white cell count indicative of inflammation and infection, though these are non-specific changes seen in other infections and inflammatory conditions (e.g. gout).

Question 20

What will observations show in a patient with septic arthritis?

Answer 20

Observations frequently show pyrexia that may be accompanied by tachycardia, on occasion haemodynamic instability is present.

Question 21

What is the gold standard for septic arthritis diagnosis?

Answer 21

Joint aspiration is the gold standard for diagnosis - where possible taken prior to antibiotic therapy. Imaging, particularly MRI, can be supportive for a diagnosis of septic arthritis.

Question 22

Joint aspiration in septic arthritis: the most important investigation. Joint fluid should be obtained prior to … It should be sent for WBC, gram stain, culture and crystal microscopy (to exclude …).

Answer 22

Joint aspiration in septic arthritis: the most important investigation. Joint fluid should be obtained prior to commencing antibiotics. It should be sent for WBC, gram stain, culture and crystal microscopy (to exclude gout/pseudogout).

Question 23

Patients with septic arthritis should be referred to and managed by ….

Answer 23

Patients with septic arthritis should be referred to and managed by orthopaedics.

Question 24

Septic arthritis management - Antibiotic management should be guided by patient factors, the suspected organism and culture results. Liaise with microbiology early. Typical courses last … weeks, with at least … weeks of intravenous therapy.

Answer 24

Septic arthritis management - Antibiotic management should be guided by patient factors, the suspected organism and culture results. Liaise with microbiology early. Typical courses last six weeks, with at least two weeks of intravenous therapy.

Question 25

What is frequently first line therapy for septic arthritis?

Answer 25

Flucloxacillin is frequently first-line therapy (clindamycin if penicillin-allergic).

Vancomycin or teicoplanin are used in cases of suspected MRSA and ceftriaxone for gonococcal arthritis or suspected gram-negative infections.

Question 26

The mortality from septic arthritis is estimated to be around …%.

Answer 26

The mortality from septic arthritis is estimated to be around 11%.