Septic arthrtis

Question 1

what is the definition of septic arthritis?

Answer 1

Septic arthritis is defined as the infection of 1 or more joints caused by pathogenic inoculation of microbes. It occurs either by direct inoculation or via haematogenous spread.

Question 2

what is the epidemiology of septic arthritis?

Answer 2

Rare

Increased Incidence in patients with underlying joint disease or prosthetic joints

Question 3

what is the aetiology of septic arthritis?

Answer 3

Septic arthritis is caused by the pathogenic inoculation of microorganisms into the joint, either directly or by the haematogenous route. The predominant causative organisms of septic arthritis are staphylococci or streptococci

Question 4

what are the risk factors for septic arthritis?

Answer 4

Underlying joint disease
Prosthetic joint
Age
Immunosuppression 
Contiguous spread
Exposure to ticks 
Previous intra articular articular corticosteroid injection, recent joint surgery, low socioeconomic status

Question 5

what is the pathophysiology of septic arthritis?

Answer 5

Following pathogenic inoculation into the joint, the mechanisms by which joint sepsis subsequently develops are as yet not fully understood. Studies in experimental mouse models have revealed a complex array of bacterial virulence factors, as well as immunological host responses, which determine the development of disease. This multiplicity of components in disease pathogenesis may explain why antibiotics alone are not always sufficient to treat joint sepsis successfully.

Question 6

what are the key presentations of septic arthritis?

Answer 6

Hot, swollen, painful, restricted joint

Acute presentation

Question 7

what are the signs of septic arthritis?

Answer 7

Hot, swollen, painful, restricted joint
Acute presentation 
Large joint affected 
Single joint affected
Prosthetic joint
Proportionality of symptoms 
Erythema migrans
Risk factors 
Sexual activity

Question 8

what are the symptoms of septic arthritis?

Answer 8

fever

Question 9

what are the first line and gold standard investigations for septic arthritis?

Answer 9

Synovial fluid microscopy via aspiration - micro-organisms may be present, urate or pyrophosphate crystals may be present
Synovial fluid cultures and sensitivities - culture may reveal organism type and sensitivities to antibiotic therapy
Synovial fluid WBC - high
Blood cultures - presence of microorganisms; subsequent culture revealing organism type and sensitivities to antibiotic therapy
WBC - high (may be normal)
ESR - high (could be normal at first, slow to go up)
CRP - high (over 100, even with RA)
Urea and electrolytes - normal or abnormal
LFTs - normal or elevated
Plain x-ray - degenerative changes
Ultrasound - presence of effusion

Question 10

what are the differential diagnoses for septic arthritis?

Answer 10

OA
Psoriatic arthritis
RA

Question 11

how is septic arthritis managed?

Answer 11

Suspected:
Follow sepsis guidelines, refer for surgery, empirical antibodies, joint aspiration, analgesia
Confirmed:
Follow sepsis guidelines, refer for surgery (aspirational washout), analgesia, pathogen-targeted antibiotics, joint aspiration, double steroid dose (prednisolone)
Unconfirmed:
Continue antibiotics if responding, refer to senior if not

Question 12

how is septic arthritis monitored?

Answer 12

After resolution of the acute illness, the patient should be followed up on at least one occasion to confirm complete recovery and to check for the presence of joint damage

Question 13

what are the complications of septic arthritis?

Answer 13

Antibiotic allergy
Osteomyelitis
Joint destruction

Question 14

what is the prognosis fo septic arthritis?

Answer 14

Delayed or inadequate treatment can lead to irreversible joint destruction and subsequent disability. There is also a single-joint estimated case fatality rate of 11%