Septic arthritis (from Bone & soft tissue infection)

Question 1

What are the potential routes of infection to cause septic arthritis?

Answer 1

Haematogenous

Eruption of bone abscess (following osteomyelitis)

Direct invasion:

• Penetrating wound (incl. from joint injections)
• Intra-articular injuries
• Arthroscopy

Question 2

How can septic arthritis happen following osteomyelitis?

Answer 2

If a septic focus ruptures:

• into sub-periosteal space - osteomyelitis cont
• into joint space - septic arthritis

Question 3

What organisms are seen in septic arthritis?

Answer 3

Staph aureus - most common as per

Strep pyogenes

Haemophilus influenzae

E.coli - predominantly in neonates or the elderly

Young & sexually active - Neisseria gonorrhoeae

Question 4

describe the pathology of acute septic arthritis?

Answer 4

Once organisms have manifested:

1) Acute synovitis develops with purulent joint effusion
* as time goes on - becomes more purulent
2) Articular cartilage is attacked by bacterial toxins and cellular enzymes produced by the neutrophils
3) If infection is left untreated - complete destruction of articular cartilage

Question 5

Describe the outcomes/sequelae of acute septic arthritis

Answer 5

If caught early & treated aggressively - recovery without damage to articular cartilage

Can have partial damage/loss of articular cartilage and subsequent development of OA over the years

If untreated - fibrous or bony ankylosis

Question 6

What is meant by ankylosing of joints following acute septic arthritis?

Answer 6

Fusion of the bones in the joint

Occurs if acute septic arthritis is not treated

Question 7

How does septic arthritis present in neonates?

Answer 7

Picture of septicaemia:

• irritable
• affected joint resistant to any movement
• ill

Question 8

Why do neonates presenting with septic arthritis get full body septic screens?

What additional investigation should be done for them?

Answer 8

Multifocal disease - so there is likely other sites of infection - usually urinary or CNS

This is why in neonates - they receive a full screen and lumbar puncture

Question 9

What are the signs of septic arthritis in neonates?

Answer 9

Acute pain in a large joint

• reluctant to move joint at all - (whereas in Bursitis the RoM is better)

Swelling of superficial joint if affected

Increased temp and pulse (inflam response)

Increased tenderness of joint

Question 10

Describe the typical presentation of septic arthritis in adults

Answer 10

Most commonly affects knee, ankle or wrist

• Acute pain in joint
• Reluctant to move
• Fever/tachycardia
• Swelling if in superficial joint
• Erythema if in late stage and in superficial joint

Question 11

How would you investigate septic arthritis?

Answer 11

FBC, WBC, ESR, CRP, blood cultures

Aspiration of synovial fluid - _{and culture of the aspirate}

Xrays - _{often normal until late-stage}

Ultrasound - _{useful for deep joints (hip and shoulder)}

MRI

Question 12

What organisms are typically found in infected joint replacements?

Answer 12

Staph epidermis

Staph aureus

Question 13

What are the differentials for septic arthritis?

Answer 13

Acute osteomyelitis

Trauma

Synovitis (irritable joint)

Haemophilia

Rheumatic fever

Gout

Gaucher’s disease

Question 14

How is acute septic arthritis treated?

Answer 14

General supportive measures

Antibiotics - start IV flucloxacillin (clindamycin if Pen allergic) then switched to oral

Aspiration to decompress joint

Arthroscopic lavage

Infected JR - stage one revision, stage two revision or just abx if caught VERY early