SEPTIC ARTHRITIS

Question 1

What is septic arthritis?

Answer 1

• inflammation of a joint secondary to infection
• should always be considered in an acutely inflamed joint as it can destroy a joint in under 24 hours and has a mortality of 11%, so is a medical emergency.

Question 2

What is the most common joint to develop SA?

Answer 2

• knee is the most common joint to develop septic arthritis. It’s usually just one joint which is extremely painful, swollen and red.
• also common in hip and shoulder but can occur in any joint

Question 3

How does the joint become infected in SA?

Answer 3

by direct injury or by blood-borne infection from an infected skin lesion or another site

Question 4

What is the most common organism that causes SA?

Answer 4

Staphylococcus aureus

Question 5

What other organisms can cause SA?

Answer 5

• Neisseria gonorrhoeae(Young adults who are sexually active)
• Staph epidermidis (more likely in prosthetic joints)
• Haemophilus influenzae in children
• Gram-NEGATIVE bacteria e.g. E.coli or Pseudomonas Aeruginosa in the elderly/very young/IVDU

Question 6

What are the risk factors of SA?

Answer 6

• Prosthetic joints
• Diabetes mellitus
• Immunosuppression e.g. HIV
• Pre existing joint disease e.g. RA (10x)
• Low socioeconomic status
• Age <15 and >55
• IVDU
• Osteomyelitis
• Intra-articular injection
• Recent joint surgery

Question 7

What are the signs of SA?

Answer 7

• Red hot swollen joint, non-weight bearing (if knee) - usually just one joint
• Tachycardic, feverish, may have a rash, malaise, anorexia.

(In the elderly and immunosuppressed and in RA the articular signs may be muted - less dramatic)

Question 8

What are the symptoms of SA?

Answer 8

Very painful joint

Early infection:
-Wound inflammation/discharge, joint effusion, loss of function and pain

-Late disease:
Presents with pain or mechanical dysfunction

Question 9

What are the differential diagnosis of SA?

Answer 9

• Crystal disease - Gout (Monosodium urate crystals) or pseudogout (Calcium pyrophosphate crystals)
• Reactive arthritis

Question 10

What are the investigations for SA?

Answer 10

• FBC – look for raised WCC
• Blood culture
• Temperature – Look for raised temp
• Urgent Joint aspiration and MCS
• Swab anything that looks like puss
• STI screen
• HIV test if suspected
• Skin wound swabs, sputum and throat swab or urine if gonococcal infection possibility
• Specialist test – TB quantification/viral PC
• X – ray: no value in SA just to rule out other causes

Question 11

What are the key investigations for SA?

Answer 11

• Joint aspiration and culture are the key investigations as the main differentials are the crystal arthropathies.
• Always urgently refer a patient if the joint affected is prosthetic.

Question 12

Describe the fluid from the aspirated joint in SA?

Answer 12

-Fluid will be purulent/opaque/thick/pussy due to high WCC in it. (Note NORMAL FLUID is clear yellow and quite thin i.e. not very viscous)

Question 13

Should you give antibiotics before joint aspiration?

Answer 13

NO!

-Always aspirate the joint before giving antibiotics

Question 14

What is the non-pharmacological treatment for SA?

Answer 14

-Joint should be immobilised early, followed by early physiotherapy to prevent stiffness and muscle wasting

Question 15

What is the pharmacological treatment for SA?

Answer 15

• Stop methotrexate and anti-TNF alpha
• IV antibiotics based on joint cultures, usually for several weeks (BNF states 6-12 weeks)
• Double prednisolone dose - ONLY IF ALREADY ON LONG TERM PREDNISOLONE

Question 16

Why do those already on prednisolone and present with SA need the dosage doubled?

Answer 16

-because in times of stress patients naturally produce lots of fight or flight hormones e.g. cortisol but in a patient who is on steroids already their adrenal glands will NOT PRODUCE this - so ALWAYS DOUBLE UP STEROIDS!

Question 17

What is the surgical treatment for SA?

Answer 17

• Needle aspiration should be used to decompress the joint

- Athroscopic lavage may be required