Infections of Joints

Question 1

Three “buckets” for thinking of bacterial joint infection

Answer 1

• Non-gonococcal
• Gonococcal (N. gonorrheae)
• Lyme (B. burgdorferi)

Question 2

Microbial Arthritis etiology table

Answer 2

Question 3

Essential Factors of Septic Arthritis

Answer 3

• Acute onset of painful, warm, swollen, usually monoarticular arthritis
• Arthrocentesis of synovial fluid >50,000 WBC / μL and >80% PMN
• Positive synovial fluid culture
• Staphylococcus aureus the most common cause

Question 4

Epidemiology of septic arthritis

Answer 4

• Higher incidence in children and elderly
• Higher incidence in individuals who already have rheumatoid arthritis
• Higher incidence in prosthetic joints
• High risk for parenteral drug use
• Diabetes mellitus is predisposing
• Immunosuppression (including corticosteroid perscription!)

Question 5

Sexual activity is a moderate risk factor for septic arthritis. Why?

Answer 5

Because it is associated with risk of gonococcal infection, which may lead to disseminated gonococcal infection (DGI), and this condition very commonly results in septic polyarticular arthritis.

Question 6

Why is it so easy for bacteria in the blood to reach the synovium?

Answer 6

1. The synovial membrane is thin and there is no basement membrane
2. The tissue is highly vascularized, and so there are many points of entry

Question 7

Without treatment, ___ may occur within days of joint infection.

Answer 7

Without treatment, irreversible subchondral bone loss and cartilage destruction may occur within days of joint infection.

Question 8

Findings of septic arthritis on physical exam

Answer 8

• Obvious joint effusion
• Inflammatory signs
• Pain
• Marked restriction of both passive and active ROM

Question 9

A patient with an acute monoarticular arthritis should be ___.

Answer 9

A patient with an acute monoarticular arthritis should be considered to have septic arthritis until proven otherwise

Question 10

__% of cases of septic arthritis involve fever.

Answer 10

60-80% of cases of septic arthritis involve fever.

So, if the patient does not present with fever, septic arthritis cannot be ruled out.

Question 11

Symptoms which indicate possibility of antecedent infection

Answer 11

• Cough
• GI symptoms
• dysuria

Question 12

Antecedent infections may be indentified in ___% of cases of septic arthritis.

Answer 12

Antecedent infections may be indentified in 50% of cases of septic arthritis.

Question 13

Passive motion of the adjacent joint usually does not elicit severe pain unless . . .

Answer 13

Passive motion of the adjacent joint usually does not elicit severe pain unless there is stretching of an inflamed tendon

Question 14

While synovial fluid analysis is critical for the definitive diagnosis of septic arthritis, . . .

Answer 14

While synovial fluid analysis is critical for the definitive diagnosis of septic arthritis, arthrocentesis is contraindicated if the needle must pass through an area of cellulitis, a skin lesion, or any lesion which may further introduce bacteria into the joint space.

Question 15

Synovial fluid analysis for suspected septic arthritis

Answer 15

• Appearance: Color and clarity (purulence and turbidity suggest infection)
• Cell count and differential
• Gram stain (positive is diagnostic, negative does not rule out septic arthritis)
• Culture (positive is diagnostic, negative does not rule out septic arthritis)

Question 16

Table of common nongonococcal septic arthritis etiologies

Answer 16

Question 17

Plain radiographs for septic arthritis

Answer 17

Not very useful, but are done specifically to rule out contiguous osteomyelitis. May show bony changes due to inflammation in late septic arthritis (8 days out or later)

Question 18

Elements of history which may suggest crystal arthropathy over infection

Answer 18

• History of recurrent monoarthritis (gout or pseudogout)
• Typical podagra (gout)
• Radiologic evidence of chondrocalcinosis (pseudogout)

Question 19

Major complications of septic arthritis

Answer 19

• Osteomyelitis
• Persistent or recurrent infection
• Decrease in joint mobility
• Aknylosis
• Persistent pain

Question 20

Essential factors of disseminated gonococcal infection

Answer 20

• Sexually active young person without history of joint disease
• Triad of polyarthritis, tenosynovitis, dermatitis
• Negative synovial fluid gram stain and culture
• Urethral, cervical, pharyngeal, and rectal testing for Neisseria gonorrhoeae in aggregate are positive in up to 90% of cases

Question 21

The time from sexual contact to the onset of DGI varies from ___ to ___.

Answer 21

The time from sexual contact to the onset of DGI varies from 1 day to 2 months

Question 22

The disseminated gonococcal infection triad

Answer 22

polyarthritis, tenosynovitis, and dermatitis

Question 23

N. gonorrheae infection accounts for __% of monoarticular septic arthritis.

Answer 23

N. gonorrheae infection accounts for 20% of monoarticular septic arthritis.

It usually presents as oligo- or poly-articular

Question 24

Course of DGI

Answer 24

• Initially presents as fever, chills, and polyarthralgia
• Progresses to frank monoarthritis or polyarticular arthritis in knees, ankles, or wrists
• Migratory tenosynovitis occurs in 2/3 of patients, usually over hand dorsum, wrist, ankle, knee
• Painless skin lesions observed in 2/3 of patients, but may go unnoticed by patient

Question 25

Laboratory findings for DGI

Answer 25

* **Blood culture**: Positive in only 20-30% of patients * **Synovial culture**: Positive in 20-50% of patients * **Synovial cell count and differential**: 30,000 - 60,000 WBC/μL * **Synovial Gram stain**: Positive in less than 25% of patients with DGI * **Nucleic acid amplification tests** on urethrum, cervix, pharynx, rectum: 90% sensitive * Imaging: Not particularly helpful

Question 26

Treatment of gonococcal septic arthritis

Answer 26

* **Closed drainage of purulent effusions** required once or twice * **Antibiotics quite effective** in eliminating residual *Neisseria* * Prognosis very favorable in all patients who receive antibiotics, **complete recovery in virtually all patients**

Question 27

Essentials factors of Lyme arthritis

Answer 27

* Reasonable risk of *B. burgdorferi* exposure in history or exam * Characteristic complex of Lyme symptoms (Stage I, Stage II, Stage III) * Supporting *B. burgdorferi* serology present in most cases, but not in very early infection

Question 28

Reasons *B. burgdorferi*-mediated disease is difficult to clear

Answer 28

1. Downregulates major antigens (the spirochete lipoproteins) upon host residence 2. Exhibits antigenic variation in VIsE protein 3. Possess lipoproteins which bind Factor H and inhibit complement activation 4. Residual pro-inflammatory products may persist even after *B. burgdorferi* is gone

Question 29

*Borrelia burgdorferi-*mediated disease

Answer 29

Cause **Lyme disease**. Begins as **local** infection and spreads to form **erythemia migrans** (bull's eye). This is indicative ot **stage I** Lyme disease. Within **days to weeks**, infection may **spread via the blood** to distant sites. The first metastasis is indicative of **stage II** Lyme disease. Cardiac involvement may lead to atrioventricular block or myopericarditis. After months to years of latent infection, spirochetes may appear in the joints, nervous system, or skin. This is indicative of **stage III** Lyme disease. Repeated episodes of **pauciarticular arthritis** are a common presentation.

Question 30

Lyme disease diagram

Answer 30

Question 32

Stage I Lyme clinical presentation - Early Localized Infection

Answer 32

* EM in 80% of patients, appears \<30 days following infection, usually ~7-10 days * Systemic flu-like symptoms: Fever, malaise, neck pain/stiffness, arthralgia, myalgia

Question 33

Stage II Lyme clinical presentation - Acute Dissemianted Disease

Answer 33

* **Weeks to months** of initial infection * May present in many sites, but most commonly: **Skin (multiple EM, sometimes necrotizing), heart (conduction system abnormalities), MSK system (pauciarticular arthritis), nervous system (Lyme nervous triad)** * **Persistent, debilitating fatigue and malaise** * Local symptoms may be **intermittent**

Question 34

Lyme nervous triad

Answer 34

1. **Aseptic meningitis** 2. **Cranial neuropathy** (usually **facial nerve** - CNVII) 3. Painful, **peripheral radiculoneuropathy** (neuropathy affecting nerve roots)

Question 35

Stage III Lyme clinical presentation - Late Persistent Disease

Answer 35

* Occurs in less than 10% of Lyme patients * Manifests in **skin (multiple EM)**, **joints** (usually **chronic monoarticular**, especially the **knee**, may be due to residual antigen), **nervous system** (**cognitive dysfunction, meningoencephalitis, sensorimotor neuropathy**)

Question 36

Laboratory findings of Lyme arthritis

Answer 36

* **Synovial WBC count and differential:** **2,000 - 100,000 WBC / μL, neutrophil predominance** * Culture: Rare to culture from Lyme patients, not much utility * **Serologic tests**: Positive *B. burgdorferi* **IgM (2-3 weeks post-infection) or IgG (\>1 month post-infection)** supports diagnosis in patients with **\>4 weeks of suggestive signs/symptoms** * **Western blot of host serum against purified *B. burgdorferi* antigen** supports diagnosis * Radiographic imaging: Used to rule out other diagnoses

Question 37

Essential features of Parvoviral Arthritis

Answer 37

* **In children**, **parvovoris B19 / erythrovirus causes erythema infectosum.** * Classic finding is a **"slapped-cheek" facial rash** * **Minority of childhood cases involve joints** * **In adults**, acute erythrovirus infection is associated with **self-limited, symmetric polyarthritis** that closely resembles rheumatoid arthritis * Diagnosis confirmed by detection of **anti-B19 antibody** in serum

Question 38

Erythrovirus epidemiology

Answer 38

* Aerosol or respiratory secretion transmission * Cyclic outbreaks worldwide, winter and spring * Children main vector for transmission, and day care workers and school workers are major at-risk population of adult cases

Question 39

Erythrovirus course

Answer 39

Question 40

Parvovirus-mediated damage

Answer 40

* Enters via respiratory tract * Infection of erythroid precursors * ~5 day viremic phase, flu-like symptoms (fever, malaise, cough, etc) * Appearance of IgM marks ending of viremic phase, ~1-1.5 weeks after exposure * IgG ~2 weeks after exposure * This is around when arthralgia/arthritis appear

Question 41

Clinical findings of parvoviral arthritis

Answer 41

* **8% of children, 50-60% of adults** experience joint symptoms * **Typically ~2 weeks post-exposure, ~1 week post flu-like symptom onset** * **Women** more commonly experience joint symptoms than men * **Symmetric** joint pattern consistent with typical **RA pattern** * **"slapped-cheek"** rash in **20%** of patients, but **general** **rash in 75%** * Most **symptoms subside on their own in 2-3 weeks**, arthralgia may remain longer in absence of permanent joint damage

Question 42

Laboratory findings of parvoviral arthritis

Answer 42

* ESR and CRP usually unaffected, not reliable metrics * Diagnosis dependent upon anti-B19 antibody detection (IgG and/or IgM) * Almost all infected patients demonstrate antibody response

Question 43

Treatment of parvoviral arthritis

Answer 43

Given the **self-limited course** of the disease, only **symptomatic therapy** is recommended (eg, **simple analgesics or NSAIDs**)