Clinical Case: Knee Pain

Question 1

Reactive arthritis

Answer 1

Acute asymmetric arthritis following urethritis (chlamydia) or gastroenteritis
6 weeks after infection
Joints of legs (knees)
May also get conjunctivitis + urethritis = Reiter’s syndrome

Question 2

Septic arthritis (monoarticular) - two organisms

Answer 2

Staph aureus - most common overall, patients usually have pre-existing joint problem or IV drug users
Neisseria gonorrhoeae - most common organism under age 30

Joint aspiration to know

Question 3

Dx of GC arthritis

Answer 3

H/P
Lab - WBC high (above 10,000)
blood cultures frequently positive (not always)
joint aspiration shows WBC over 100,000 (not specific)
Gram stain and culture PRIMARY

Question 4

tx of GC arthritis

Answer 4

3rd gen cephalosporin
oral macrolide abs (azithromycin) also indicated for presumptive tx of chlamydia
prognosis usually good w/ rapid resolution of sxs and signs

Question 5

Septic arthritis commonly caused by

Answer 5

Staph aureus

or Neisseria gonorrhoeae

Question 6

Urethritis, conjunctivitis and monoarthritis is called

Answer 6

Reiters syndrome

Question 7

Gout

Answer 7

Uric acid crystals precipitate in joint
Very acute onset
Most common site in great toe
Low grade fever

Question 8

Pseudogout

Answer 8

Looks same as gout
Cause: calcium pyrophosphate crystal deposition
Can involve same joints (feet, knee, wrist, ankle) + Shoulder and hips

Question 9

acute monoarticular arthritis definition

Answer 9

acute joint inflammation that occurs days or less before seeking attention

Question 10

acute monoarticular arthritis differential

Answer 10

gout, pseudogout, reactive arthritis, septic arthritis

Question 11

Gout dx

Answer 11

Dx: joint aspiration, polarized light demonstrates negatively birefringent crystals

Question 12

pseudogout dx

Answer 12

Dx: Joint aspiration, positive birefringent crystals

Question 13

Reiter’s syndome

Answer 13

Reactive arthritis + conjunctivitis +urethritis

Question 14

GC arthritis - two musculoskeletal syndromes form disseminated GC

Answer 14

Arthritis-dermatitis syndrome - arthralgias, skin lesions, inflammation of tendons
Localized septic arthritis - septic arthritis and bacteremia rarely found at same time (knee most common)

Question 15

Neisseria gonorrhoeae

Answer 15

bacteria - gram (-) - diplococci - oxidase (+) - only glucose oxidizer

Question 16

Neisseria gonorrhoeae virulence factors

Answer 16

specialized pilli - allows attachment to mucosal surface, antigenic variation to evade host defenses, prevents phagocytosis
Endotoxic
Capsule
IgA protease

Question 17

Media used for isolated N. gonorrhoeae

Answer 17

Thayer-Martin

Question 18

Most common cause of septic arthritis in sexually active people

Answer 18

N. gonorrhoeae

Question 19

NG pathogenesis

Answer 19

attach via pili to mucosal cells of urethra and vagina - evades mucosal IgA Ab via IgA protease. Endocytosed by cells. Kills cilliated cells. –> inflammatory response leading to urethritis and cervicitis.