Septic arthritis

Question 1

Definition

Answer 1

Infection of the joint

Typically affecting a single joint (mono arthritis)

it is a medical emergency and should be diagnosed as soon as possible and treated as soon as possible

> 24 hours–>irreversible damage

Question 2

Aetiology

Answer 2

Bacterial infections (staphylococcus aureus, group A streptococcus, neisseria gonorrhoea)

viruses

fungi

parasites

most commonly from haematogenous spread but can be infection/trauma

Question 3

Pathogenesis

Answer 3

Skin infection- normally staphylococcus aureus can disseminate into the joint causing septic arthritis

Osteomyelitis- normally caused by staphylococcus aureus, can attack the joint from locally

Upper and lower respiratory tract infections- usually caused by group A streptococcus, can haematogenously move to the bone, causing osteomyelitis which can eventually cause septic arthritis

STI- caused by neisseria gonorrhoeae, that can disseminate into the blood causing septic arthritis

procedures on the joint- can introduce bacteria into the joint causing septic arthritis

Question 4

Risk factors

Answer 4

Artificial joint

Other types of arthritis being present

Diabetes

Old age

Immunosuppressive meds

Recent joint injury

Question 5

Clinical presentation

Answer 5

Pain

Swelling

Heat

Redness

Reluctance to move affected limb

ROM decrease

Pyrexia (raised body temperature)

Monoarthritis (main diagnostic feature)

Question 6

Investigations

Answer 6

Blood biochemistry- raised ESR, raised CRP to check for signs of inflammation (inflammatory markers)
– can also do a blood test to see any infection in the blood.

Joint aspiration:
– to differentiate between septic arthritis and gout
— if there’s no bacteria present, then it shouldn’t be infectious and the diagnosis shouldn’t be septic arthritis
– might mean possibility of gout

Imaging:
– x rays and other imaging test of the affected joint can be done to assess the damage to the joint or loosening of an artificial joint
—- joint space widening because of the swelling and inflammation on the joint

Question 7

Treatment

Answer 7

Antibiotics:
– can be tailored with the results of the blood test to fight against the causative agent (2 weeks IV, followed by 4 weeks oral)

Joint drainage:
– removing the infected fluid from the joint is crucial
– needle- inserting a needle into the joint space
– scope procedure- arthroscopy, suction and drainage tubes are placed down the little incisions to drain the fluid
– open surgery- some joint (hip), are more difficult to drain with a needle or arthroscopy, so an open procedure might be necessary

Removal of replacement joint:
– if an artificial joint is infected, treatment often involves removing the joint and temporarily replacing it with a joint spacer (a device with antibiotic cement). Several months later, a new replacement joint is implanted.