Acute Arthritis/Osteomyelitis

What is the difference between arthritis, arthralgia and tenosynovitis?

1) Arthritis is inflammation of a joint and have characteristic features such as
→ pain
→ swelling
→ warmth
→ erythema
→ typically lasts less than 6 weeks

2) Arthralgia is pain in a joint 
→ not all pain in the joint is associated with arthritis 

3) Tenosynovitis is inflammation of the tendon sheath

How is arthritis classified based on joint involvement

1) Monoarticular
→ a single joint is involved

2) Oligoarticular
→ at least 2-3 joints involved and typically presents asymmetrically

3) Polyarticular
→ multiple joints are involved and presents both symmetrically and asymmetrically
→ there are several different subtypes such as ones that start in one place and spread (migratory) or occur simultaneously

What is the microbiological pathophysiology of acute arthritis?

Arthritis involves activation of both innate and adaptive immunity

1) Macrophages and specifically neutrophils are recruited to the articular tissue by receptor activation
→ the neutrophils will activate NADPH oxidase leading to the formation of reactive oxygen species
→ they will generate eicosanoids inducing inflammation
→ they will release lysosomal enzymes and proteases which will degrade the cartilage

2) Adaptive immune response is also triggered through recruitment of T and B-cells
→ T-cells will promote neutrophil recruitment and activation of monocytes
→ B-cells will produce antibodies forming immune complexes that activate complement in the tissue leading to inflammation

3) Persistent antigen expression can lead to persistent T and B-cell activation causing persistent inflammation

What is Septic Arthritis? What are the Characteristic Features and Findings?

Septic or bacterial arthritis is a monoarticular form of arthritis

1) Patients will have classic presentation of arthritis with additional fever 
→ most commonly caused by hematogenous seeding of the joint (spread from the blood) from the organism
→ is often seen in patients who already have arthritis, use IV drugs, or are on immunosuppressed

2) This process is rapidly destructive and can lead to permanent joint damage unless treated within 4-5 days
→ can see periarticular osteopenia or reduced bone mass around the joint
→ later on you can see infection of the adjacent bone leading to secondary osteoarthritis

3) When drawing fluid from the area, it will be purulent, have a high WBC count that is predominantly neutrophils, and will have the organism appear on gram-stain

What kinds of bacteria most commonly cause septic arthritis?

The causative organism for septic arthritis will vary by age and risk factors and where they affect

1) Kids
→ MSSA/MRSA (Staph Aureus)

2) Teenagers/Young Adults
→ Neisseria Gonorrhoeae

3) Adults
→ if they have a gram positive infection it is more likely to be staphylococci
→ if gram negative it can be E. coli or pseudomonas

4) IV Drug Users
→ have a higher risk for staphylococci from your skin and pseudomonas from tap water, commonly affecting the sternoclavicular joints

5) Sacroiliac Joints
→ Brucellosis due to ingestion of unpasteurized milk

What is Disseminated Gonococcal Infection

Disseminated Gonococcal Infection is caused by infection of Neisseria Gonorrhea and is a common cause of septic arthritis in teenagers

1) This disease will have a lack of genitourinary symptoms and will have two major presentation patterns
→ Tenosynovitis (inflammation of the tendon) with additional migratory arthralgias and skin pustules on a erythematous base
→ Suppurative (pus) monoarthritis/oligoarthritis

2) If you suspect a patient has this you should obtain a culture on Thayer-Martin Chocolate Agar
→ treated with a combination of Ceftriaxone + Azithromycin/Doxycycline

What would it mean if someone has recurrent gonococcal or meningococcal infections?

Recurrent infections with Neisseria is associated with a complement deficiency with the most common being C5, C6, or C8 deficiencies
→ screened with a low CH50 level

What is Bacterial Endocarditis?

Bacterial Endocarditis is an infection of the endocardium of the heart which can lead to an acute or subacute presentation of polyarticular arthritis

1) Bacterial Endocarditis can cause arthritis through immune complex deposition in the joints and may cause patients to present with:
→ Osler’s Nodes - tender nodules that are caused by immune complex deposition, often painful
→ Janeway lesions - flat macules that are caused by septic emboli
→ mucosal hemorrhages
→ splinter hemorrhages in the nail beds

2) Can classically have anemia, proteinuria, rheumatoid factor, etc

How can Lyme Disease cause arthritis?

Lyme Disease is infection with Borrelia burgdorferi and can cause both acute and chronic arthritis

1) Acute Infection
→ erythema migrans rash
→ will have diffuse joint pain (polyarthralgias)

2) Chronic Arthritis
→ occurs weeks to months after initial infection and will lead to monoarthritis of the knee

How can parvovirus cause arthritis?

Parvovirus B-19 is a common viral infection in kids and has a varied presentation in adults and children

1) Pediatric Presentation is Erythema Infectiosum or Fifth’s Disease
→ causes a slapped cheek rash on kids

2) Adults infected are often adults that spend lots of time with children
→ will have a morbilliform or maculopapular rash
→ have symmetric articular rashes especially in the PIP, MCP, wrist and knee joints
→ the arthritis is self limited but patients will often have arthralgia that can persist up to two years

How can Hepatitis B Virus cause arthritis?

Hepatitis B can cause abrupt onset symmetric polyarthritis

1) Hepatitis B arthritis will often occur before they have jaundice but may have elevated serum transaminases on lab exam

2) The disease is associated with a urticarial skin rash and the whole process is self-limited lasting around 7-10 days
→ the rash and symmetric polyarthritis occur during viremia so you should be able to detect Hepatitis B along with low serum complement levels

What is Sarcoidosis and how can it lead to arthritis?

Sarcoidosis is a multisystem granulomatous disorder that leads to the formation of noncaseating granulomas in organs

1) The initial presentation of this disease is often arthritis in the knees and ankles
→ can also have panniculitis or inflammation of the fat behind the skin with infiltration of T-cells 
→ can also have erythema nodosum lesions 
→ can also have bilateral hilar adenopathy or inflammation of the hilar lymph nodes of the lung

What is Osteomyelitis?

Osteomyelitis is invasion of the bone by microorganisms and are classified based on the route of infection
→ hematogenously
→ contiguous spread (from a local infection)
→ trauma

1) Osteomyelitis will classically present with cardinal signs of inflammation and poor wound healing at the site of injury
→ the skin laying over the bone can be ulcered or have cellulitis features